Information disk recording/reproducing device, and method for detecting vibration of information disk recording/reproducing device

ABSTRACT

The present invention provides an information disc-recording/playback apparatus which includes a track cross detection means ( 112 ), a track cross direction detection means ( 113 ), a rotation angle detection means ( 114 ), and a count means ( 115 ), detects the track pitch of a disc, evaluates the vibration amount, or vibration speed, or vibration acceleration considering the track pitch of the disc, and determines a maximum rotation speed that is lower than the allowable vibration amplitude, vibration speed, or vibration acceleration of the information disc recording/playback apparatus; as well as a vibration detection method for the information disc recording/playback apparatus.  
     This information disc recording/playback apparatus can perform vibration detection using a single threshold value that is independent of the type of the disc, without using an acceleration sensor, and further, the apparatus can accurately perform vibration detection even when direction detection is difficult.

TECHNICAL FIELD

[0001] The present invention relates to an information discrecording/playback apparatus having a vibration measurement means formeasuring vibrations caused by an eccentricity of a disc, and avibration detection method for the information disc recording/playbackapparatus. More particularly, the invention relates to an informationdisc recording/playback apparatus having a construction for performingvibration detection using track counting.

BACKGROUND ART

[0002] In recent years, optical disc playback apparatuses have made aremarkable increase in the recording/playback speed. The optical discplayback apparatuses have achieved the increase in the playback speed byincreasing the rotation speed of optical discs.

[0003] However, when the rotation speed of an optical disc is increased,vibration due to an eccentricity of the optical disc adversely affectscontrol such as servo, resulting in a problem that the user of theoptical disc playback apparatus might feel uncomfortable. In view ofsuch problem, when an optical disc having a large eccentricity is loadedon the optical disc playback apparatus, the optical disc playbackapparatus limits the rotation speed of the disc to prevent the adverseeffect of vibration due to the disc of the large eccentricity.Therefore, measurement of vibration amplitudes is an important techniquefor preventing the adverse effect of vibration due to the disc of thelarge eccentricity in the optical disc playback apparatus.

[0004]FIG. 8 is a block diagram illustrating a conventional optical discplayback apparatus 800 having a structure for detecting vibration withan acceleration sensor. In FIG. 8, reference numeral 801 denotes a base,numeral 802 denotes a disc motor mounted on the base 801, numeral 803denotes an insulator supporting the base 801, numeral 804 denotes a discmounted on the disc motor 802, numeral 805 denotes an accelerationsensor mounted on the base 801, and numeral 806 denotes a measurementunit for measuring the amount of eccentricity on the basis of the outputof the acceleration sensor 805.

[0005] Hereinafter, the operation will be described. When the disc motor802 on which the disc 804 is mounted is rotated at a predetermined rpm,a centrifugal force in proportion to the amount of eccentricity of thedisc 804 is generated. The base 801 supported by the insulator 803vibrates at an amplitude that is determined by the amount ofeccentricity of the disc 804, the total mass of the base 801 and theconstituents mounted on the base 801, and the spring constant of theinsulator 803.

[0006] The vibration of the base 801 is converted into an electricsignal by the acceleration sensor 805 mounted on the base 801. Themeasurement unit 806 measures the vibration amplitude of the base 801 onthe basis of the electric signal obtained by the acceleration sensor805.

[0007] Then, the measured vibration amplitude is compared with a presetthreshold value, thereby determining a maximum rotation speed of thedisc mounted on the optical disc device.

[0008] Furthermore, FIG. 9 is a block diagram illustrating aconventional optical disc playback apparatus 900 performing vibrationdetection using track counting, which is disclosed in Japanese PublishedPatent Application No. 2000-113581. In FIG. 9, the same referencenumerals as those shown in FIG. 8 denote the same or correspondingparts, and reference numeral 901 denotes an optical head which issuspended over the base 801 via an elastic member 902.

[0009] Reference numeral 903 denotes a light beam applied to the disc804 from the optical head 901, and numeral 904 denotes informationrecording tracks which are concentrically or spirally formed on aninformation recording surface 804A of the disc 804 at a constant pitch.Furthermore, reference numeral 905 denotes a track cross detection unitfor generating track cross pulses and a cross direction signal fromsignals which are reproduced when the light beam 903 crosses theinformation recording tracks 904; numeral 906 denotes a count unit forcounting the track cross pulses; numeral 907 denotes a measurement unitfor determining the amount of eccentricity from the counting result ofthe count unit 906; and numeral 908 denotes a motor control unit forcontrolling the rpm of the disc motor 802, and outputting rotation angleinformation to the measurement unit 907.

[0010] The distance between the optical head 901 and the disc 804 iskept constant so that the focus of the light beam 903 is positioned onthe information recording surface 804A of the disc 804. The position ofthe optical head 901 relative to the disc 804 in the direction of theradius of the disc 804 (the direction indicated by an arrow R) hasvibration characteristics represented by a natural frequency ofvibration foA which is determined by the spring constant of the elasticmember 902 comprising a material such as metal, resin, or rubber, andthe mass of the optical head 901.

[0011] The base 801 is supported by the insulator 803 comprising amaterial such as metal, resin, or rubber. When the centrifugal forcegenerated by the rotation of the disc 804 is propagated through the discmotor 802 to the base 801, the base 801 vibrates on the basis ofvibration characteristics represented by a natural frequency ofvibration foM which is determined by the total mass of the constituentsincluding the base 801, the optical head 901 mounted on the base 801,the disc motor 802, and the disc 804, and the spring constant of theinsulator 803.

[0012] The motor control unit 908 rotates the disc motor 802 at a firstrpm that is sufficiently lower than the natural frequency of vibrationfoA. The optical disc 804 mounted on the disc motor 802 is rotated atthe first rpm.

[0013] Within the range of the first rpm that is sufficiently lower thanthe natural frequency of vibration foA, the optical head 901 vibratestogether with the base 801. The relative position between the opticalhead 901 and the optical disc 804 hardly changes. Therefore, at thefirst rpm that is sufficiently lower than the natural frequency ofvibration foA, the light beam 903 crosses a number of informationrecording tracks 904 equivalent to the amount of eccentricity of theinformation recording tracks 904. The light beam 903 generates trackcrosses as many as the information recording tracks 904 the light beam903 has crossed.

[0014] Then, the track cross detection unit 905 detects the trackcrosses corresponding to the information recording tracks 904 the lightbeam 903 has crossed, on the basis of the playback signals of theoptical head 901, and generates track cross pulses corresponding to thedetected track crosses. The track cross detection unit 905 outputs thegenerated track cross pulses to the count unit 906.

[0015] The count unit 906 counts the track cross pulses for one rotationof the disc 804 on the basis of the rotation angle information from themotor control unit 908. The measurement unit 907 stores a count resultN1 of the track cross pulses for one rotation of the disc 804, which arecounted by the count unit 906.

[0016] Next, the motor control unit 908 rotates the disc motor 802 at asecond rpm that is higher than the natural frequency of vibration foAand lower than the natural frequency of vibration foM. Then, acentrifugal force is generated in the disc 804 due to the eccentricityof the disc 804. The base 801 vibrates at an amplitude that isdetermined by the amount of eccentricity of the disc 804, the total massof the base 801 and the components mounted on the base 801, and thespring constant of the insulator 803.

[0017] When the disc motor 802 rotates at the second rpm that is higherthan the natural frequency of vibration foA and lower than the naturalfrequency of vibration foM, only the base 801, disc motor 802, and disc804 vibrate together while the optical head 901 is in the static state.Therefore, the relative displacement between the disc 804 and theoptical head 901 becomes equal to the vibration displacement of the base801. As a result, the light beam 903 generates track crosses as many asthe tracks equivalent to an amount in which the vibration amplitude ofthe base 801 is added to the amount of eccentricity of the informationrecording tracks 904.

[0018] The track cross detection unit 905 detects the track crosses asmany as the tracks equivalent to the amount comprising the amount ofeccentricity of the information recording tracks 904 and the vibrationamplitude of the base 801, and generates track cross pulses as may asthe tracks equivalent to the amount comprising the amount ofeccentricity of the information recording tracks 904 and the vibrationamplitude of the base 801. The track cross detection unit 905 outputsthe generated track cross pulses to the count unit 906.

[0019] The count unit 906 counts the track cross pulses for one rotationof the disc 804, on the basis of the rotation angle information from themotor control unit 908. The measurement unit 907 subtracts the countresult N1 from a count result N2 obtained by the count unit 906, therebyobtaining the vibration amplitude of the base 801 alone.

[0020] Then, the measured vibration amplitude is compared with athreshold value which is prepared for each disc type, therebydetermining a maximum rotation speed of the disc loaded on the opticaldisc device.

[0021] Furthermore, when detecting a vibration amplitude by a trackcounting method, setting of a track count filter according to thevibration speed becomes important for preventing false count. Although amethod of setting a track count filter for vibration detection is notgeneral at present, a method disclosed in Japanese Published PatentApplication No. Hei. 8-45089 is known as a method of setting a trackcount filter at seeking. To be specific, an optical disc devicedisclosed is provided with a PLL circuit for outputting a controlfrequency according to the moving speed of an optical head when theoptical head is moved to a target track position on the surface of anoptical disc by a thread motor; an F/V conversion circuit for convertingthe control frequency into a voltage; and a ripple detection filter forattenuating a noise component included in a ripple signal from anenvelope detection circuit, whose filter characteristic is changedaccording to the voltage from the F/V conversion circuit. Thereby, thecut-off frequency of the filter is varied according to the moving speedof the optical head.

[0022] In the above-mentioned conventional method for detectingvibration using the acceleration sensor 805, since the vibration itselfof the disc device is measured using the acceleration sensor, a maximumrotation speed can be determined by comparing the measurement resultwith a single threshold value that is independent of the disc type.However, an increase in cost due to mounting of the acceleration sensor805 and a signal amplifier for amplifying the signal from theacceleration sensor 805 is considerable. Furthermore, it is necessary tosecure a space for mounting the acceleration sensor 805 and the signalamplifier.

[0023] Furthermore, in the conventional method for detecting vibrationusing track counting, which is disclosed in Japanese Published PatentApplication No. 2000-113581, measurement of vibration amplitudes can becarried out with reduced cost and space, without using an accelerationsensor. However, since track counting is employed, if the track pitch ofthe disc varies, the value of the measured vibration amplitude alsovaries even under the same vibration condition and, therefore, athreshold value must be prepared for each of discs having differenttrack pitches, and a maximum rotation speed is determined by comparisonwith each threshold value. However, the vibration of the disc devicevaries depending on the setting condition of the disc device on asystem, and moreover, the vibration amplitude with which the user feelsuncomfortable depends on the human sense and so it varies depending onthe user. Therefore, a threshold value must be set for each system onwhich the disc device is to be mounted. However, since threshold settingvaries depending on the loading condition or the like of the disc to beused on the disc device, a large amount of data must be measured, andthe amount of data further increases according to the number of disctypes, whereby enormous time is required.

[0024] Furthermore, in the method of setting a track count filterdisclosed in Japanese Published Patent Application No. Hei. 8-45089,when performing traverse seek, how the seek speed will change is knownin advance because acceleration or deceleration of the seek speed iscarried out according to a speed profile that has previously beendetermined, and the response speed to the change in the filtercharacteristics can be appropriately set according to the predeterminedprofile. However, in the case where the frequency and the speed changein the frequency are changed considerably due to the eccentricity of thedisc or the vibration amplitude like the track count pulses forvibration detection, it is difficult to set the response speed to thechange in the filter characteristics, resulting in false count when theresponse speed is too high or too low.

[0025] The present invention is made to solve the above-describedproblems and has for its object to provide an information discrecording/playback apparatus and a vibration detection method for theinformation disc recording/playback apparatus, which can measurevibration amplitudes with reduced cost and space without using anacceleration sensor, perform vibration detection using a singlethreshold value that is independent of the disc type, and performaccurate vibration detection even when direction detection is difficult.

[0026] It is another object of the present invention to provide aninformation disc recording/playback apparatus and a vibration detectionmethod for the information disc recording/playback apparatus, which canprovide a method of controlling the cut-off frequency of a noise removalfilter for track counting most suited to vibration detection, andperform accurate vibration detection with less false count.

[0027] Measures to Solve the Problems

[0028] According to claim 1 of the present invention, there is providedan information disc recording/playback apparatus capable of recording orplaying at least two kinds of information discs having different trackpitches, on which information recording tracks are formed spirally orconcentrically, which apparatus comprises: a disc rotation means forrotating the information disc at a predetermined speed; a reading meansfor reading an information signal from the disc; a drive means fordriving the reading means in the direction of the radius of the disc; atrack pitch detection means for detecting the track pitch of theinformation disc from the information disc; a track cross detectionmeans for generating track cross signals on the basis of playbacksignals that are generated when the reading means crosses theinformation tracks; a count means for counting track cross pulses thatare detected by the track cross detection means, and outputting thecount; and a control means for determining a maximum rotation speed thatis lower than an allowable vibration amplitude of the information discrecording/playback apparatus on the basis of the count and the trackpitch, or determining a maximum rotation speed that is lower than anallowable vibration speed or vibration acceleration speed of theinformation disc recording/playback apparatus on the basis of the count,the track pitch, and the current disc rotation speed, and controllingthe disc rotation means so that the disc rotation means rotates theinformation disc at a speed lower than the allowable maximum rotationspeed to record or reproduce data in/from the disc.

[0029] According to claim 2 of the present invention, the informationdisc recording/playback apparatus defined in claim 1 further comprises:a track cross direction detection means for detecting a track crossdirection indicating the direction in which the reading means crossesthe information tracks; a rotation angle detection means for outputtingrotation angle information of the disc rotation means; and the countmeans for counting the track cross pulses with signs, which are detectedby the track cross detection means, on the basis of the result of thedetection by the track cross direction detection means, and the rotationangle information outputted from the rotation angle detection means.

[0030] According to claim 3 of the present invention, the informationdisc recording/playback apparatus defined in claim 1 further comprises:a track cross direction detection means for detecting a track crossdirection indicating the direction in which the reading means crossesthe information tracks; a track cross speed detection means fordetecting the frequency of the track cross pulses; a rotation angledetection means for outputting rotation angle information of the discrotation means; and the count means for counting the track cross pulseswith signs, which are detected by the track cross detection means, onthe basis of the result of the detection by the track cross directiondetection means and the rotation angle information outputted from therotation angle detection means, while detecting the track crossdirection by the track cross direction detection means when the resultof the detection by the track cross speed detection means indicates thatthe track cross speed is lower than a predetermined value, and countingthe track cross pulses with signs, without detecting the track crossdirection by the track cross direction detection means, on the basis ofthe track cross direction that has just previously been detected by thetrack cross direction detection means, when the result of the detectionby the track cross speed detection means indicates that the track crossspeed becomes higher than the predetermined value.

[0031] According to claim 4 of the present invention, there is providedan information disc recording/playback apparatus capable of recording orplaying at least two kinds of information discs having different trackpitches, on which information recording tracks are formed spirally orconcentrically, which apparatus comprises: a disc rotation means forrotating the information disc at a predetermined speed; a reading meansfor reading an information signal from the disc; a drive means fordriving the reading means in the direction of the radius of the disc; atrack pitch detection means for detecting the track pitch of theinformation disc from the information disc; a track cross detectionmeans for generating track cross signals on the basis of playbacksignals that are generated when the reading means crosses theinformation tracks; a track cross direction detection means fordetecting a track cross direction indicating the direction in which thereading means crosses the information tracks; a rotation angle detectionmeans for outputting rotation angle information of the disc rotationmeans, which is divided into n areas for one rotation; a zero cross areadetection means for detecting two areas where the track cross speed hasa lowest value, from among the n areas; a count means for counting trackcross pulses with signs, which are detected by the track cross detectionmeans, on the basis of the result of the detection by the track crossdirection detection means and the rotation angle information outputtedfrom the rotation angle detection means, while detecting the track crossdirection by the track cross direction detection means, in an area wherethe track cross speed has the lowest value according to the result ofthe detection by the zero cross area detection means, counting the trackcross pulses with signs, without detecting the track cross direction bythe track cross direction detection means, on the basis of the trackcross direction that has just previously been detected by the trackcross direction detection means, in an area where the track cross speeddoes not have the lowest value according to the result of the detectionby the zero cross area detection means, and outputting the count; and acontrol means for determining a maximum rotation speed that is lowerthan an allowable vibration amplitude of the information discrecording/playback apparatus on the basis of the count and the trackpitch, or determining a maximum rotation speed that is lower than anallowable vibration speed or vibration acceleration speed of theinformation disc recording/playback apparatus on the basis of the count,the track pitch, and the current disc rotation speed, and controllingthe disc rotation means so that the disc rotation means rotates theinformation disc at a speed lower than the allowable maximum rotationspeed to record or reproduce data in/from the disc.

[0032] According to claim 5 of the present invention, there is providedan information disc recording/playback apparatus capable of recording orplaying at least two kinds of information discs having different trackpitches, on which information recording tracks are formed spirally orconcentrically, which apparatus comprises: a disc rotation means forrotating the information disc at a predetermined speed; a reading meansfor reading an information signal from the disc; a drive means fordriving the reading means in the direction of the radius of the disc; atrack pitch detection means for detecting the track pitch of theinformation disc from the information disc; a track cross detectionmeans for generating track cross signals on the basis of playbacksignals that are generated when the reading means crosses theinformation tracks; a track cross direction detection means fordetecting a track cross direction indicating the direction in which thereading means crosses the information tracks; a rotation angle detectionmeans for outputting rotation angle information of the disc rotationmeans, which is divided into n areas for one rotation; a zero cross areadetection means for detecting two areas where the track cross speed hasa lowest value, from among the n areas; a count means including a firstcount means for counting track cross pulses with signs, which aredetected by the track cross detection means, on the basis of the resultof the detection by the track cross direction detection means and therotation angle information outputted from the rotation angle detectionmeans, and a second count means for counting the track cross pulsesdetected by the track cross detection means, without detecting the trackcross direction, on the basis of the rotation angle informationoutputted from the rotation angle detection means, which count meansobtains a first count of the first count means when the drive means isdisabled and the information disc loaded on the disc rotation means isrotated, obtains a second count in which a sign is added to the count ofthe second count means, on the basis of the track cross direction whichhas just previously been detected by the track cross direction detectionmeans, when the drive means is disabled and the information disc loadedon the disc rotation means is rotated, selects the first count in anarea where the track cross speed has the lowest value according to theresult of the detection by the zero cross area detection means, selectsthe second count in an area where the track cross speed does not havethe lowest value according to the result of the detection by the zerocross area detection means, and counts the track cross pulses for everyrotation angle and outputting it; and a control means for determining amaximum rotation speed that is lower than an allowable vibrationamplitude of the information disc recording/playback apparatus on thebasis of the counts and the track pitch, or determining a maximumrotation speed that is lower than an allowable vibration speed orvibration acceleration speed of the information disc recording/playbackapparatus on the basis of the counts, the track pitch, and the currentdisc rotation speed, and controlling the disc rotation means so that thedisc rotation means rotates the information disc at a speed lower thanthe allowable maximum rotation speed to record or reproduce data in/fromthe disc.

[0033] According to claim 6 of the present invention, in the informationdisc recording/playback apparatus defined in claim 4 or 5, the rotationangle detection-means divides the rotation angle information of the discrotation means into six areas for each rotation, and outputs the dividedinformation; and the zero cross area detection means detects, as zerocross areas, an area where the count of the count means has the smallestvalue, and an area on a diagonal line with respect to the area.

[0034] According to claim 7 of the present invention, there is providedan information disc recording/playback apparatus capable of recording orplaying at least two kinds of information discs having different trackpitches, on which information recording tracks are formed spirally orconcentrically, which apparatus comprises: a disc rotation means forrotating the information disc at a predetermined speed; a reading meansfor reading an information signal from the disc; a drive means fordriving the reading means in the direction of the radius of the disc; atrack pitch detection means for detecting the track pitch of theinformation disc from the information disc; a track cross detectionmeans for generating track cross signals on the basis of playbacksignals that are generated when the reading means crosses theinformation tracks; a count means for counting track cross pulses thatare detected by the track cross detection means, and outputting thecount; and a control means for, using, as the count, a differencebetween the track cross count that is obtained when the information discis rotated at a first rotation speed and at least one rotation speedthat is higher than the first rotation speed, and a count that ismeasured with the at least one rotation speed higher than the firstrotation speed, determining a maximum rotation speed that is lower thanan allowable vibration amplitude of the information discrecording/playback apparatus on the basis of the count and the trackpitch, or determining a maximum rotation speed that is lower than anallowable vibration speed or vibration acceleration speed of theinformation disc recording/playback apparatus on the basis of the count,the track pitch, and the current disc rotation speed, and controllingthe disc rotation means so that the disc rotation means rotates theinformation disc at a speed lower than the allowable maximum rotationspeed to record or reproduce data in/from the disc.

[0035] According to claim 8 of the present invention, in the informationdisc recording/playback apparatus defined in claim 7, the first rotationspeed is a sufficiently low speed at which no vibration occurs betweenthe information disc and the reading means, and the track cross pulsesdue to the eccentricities of the information disc and the disc rotationmeans are counted.

[0036] According to claim 9 of the present invention, in the informationdisc recording/playback apparatus defined in claim 7, the count meanscounts the track cross pulses at the first rotation speed for apredetermined number of times, and counts the track cross pulses withthe at least one rotation speed that is higher than the first rotationspeed, for the predetermined number of times; and the control meansemploys, as the count, an average of counts for more than one time,which are selected from among the counts obtained by the above-describedrepetition, or a value in proportion to the average.

[0037] According to claim 10 of the present invention, in theinformation disc recording/playback apparatus defined in claim 7, therotation angle detection means outputs the rotation angle information ofthe disc rotation means, which is divided into six areas for onerotation, and when a difference between the track cross count measuredat the first rotation speed with each of the six-divided rotationangles, and the track cross count which is measured with the at leastone rotation speed higher than the first rotation speed is as follows:

[0038] DAT[n]=DAT[0],DAT[1],DAT[2],DAT[3],DAT[4],DAT[5]

[0039] (when n>5, n=n mod 6 (a remainder of n being divided by 6), thecontrol means determines a maximum rotation speed that is lower than theallowable amplitude of the information disc recording/playbackapparatus, on the basis of a value in proportion to a vibration amount 1or a vibration amount 2, or a value in proportion to the second power ofthe vibration amount 1 or the second power of the vibration amount 2,and the track pitch, the vibration amounts 1 and 2 being represented asfollows: $\begin{matrix}{{{vibration}\quad {amount}\quad {1\lbrack n\rbrack}} = {\frac{2}{\sqrt{3}}\quad \sqrt{| {{{DAT}\lbrack n\rbrack}^{2} + {{{DAT}\lbrack n\rbrack}{{DAT}\lbrack {n + 1} \rbrack}} + {{DAT}\lbrack {n + 1} \rbrack}^{2}} |}}} & ( {{Formula}\quad 12} ) \\{{{vibration}\quad {amount}\quad {2\lbrack n\rbrack}} = {\frac{2}{\sqrt{3}}\sqrt{| {{{DAT}\lbrack n\rbrack}^{2} - {{{DAT}\lbrack n\rbrack}{{DAT}\lbrack {n + 2} \rbrack}} + {{DAT}\lbrack {n + 2} \rbrack}^{2}} |}}} & ( {{Formula}\quad 13} )\end{matrix}$

[0040] According to claim 11 of the present invention, in theinformation disc recording/playback apparatus defined in claim 10, thecontrol means determines a maximum rotation speed that is lower than theallowable amplitude of the information disc recording/playbackapparatus, on the basis of a value in proportion to an average of twelvevibration amounts 1 or vibration amounts 2 which are calculated forn=0˜5 according to (Formula 12) or (Formula 13), and the track pitch, ora value in proportion to an average of m pieces of central valuesselected from among the twelve vibration amounts 1 or vibration amounts2, and the track pitch, or a value in proportion to an average of mpieces of central values selected from the second powers of the twelvevibration amounts 1 or vibration amounts 2, and the track pitch.

[0041] According to claim 12 of the present invention, in theinformation disc recording/playback apparatus defined in claim 7, therotation angle detection means divides the rotation angle information ofthe disc rotation means into six areas for one rotation, and outputs thedivided rotation angle information; and when a difference between thetrack cross count which is obtained at the first rotation speed for eachof the six-divided rotation angles, and the track cross count which isobtained with the at least one rotation speed higher than the firstrotation speed is represented by

[0042] DAT[n]=DAT[0],DAT[1],DAT[2],DAT[3],DAT[4],DAT[5]

[0043] (when n>5, n=n mod 6 (a remainder of n being divided by 6), andthe rotation speed of the disc rotation means is Vrpm[rpm], the controlmeans determines a maximum rotation speed that is lower than theallowable amplitude of the information disc recording/playbackapparatus, on the basis of a value in proportion to a vibration speed 1or a vibration speed 2, or a value in proportion to the second power ofthe vibration speed 1 or the second power of the vibration speed 2, andthe track pitch, the vibration speeds 1 and 2 being represented by$\begin{matrix}{{{vibration}\quad {speed}\quad {1\lbrack n\rbrack}} = {\frac{{2\pi \quad V_{rpm}}\quad}{60}\quad \frac{2}{\sqrt{3}}\quad \sqrt{| {{{DAT}\lbrack n\rbrack}^{2} + {{{DAT}\lbrack n\rbrack}{{DAT}\lbrack {n + 1} \rbrack}} + {{DAT}\lbrack {n + 1} \rbrack}^{2}} |}}} & ( {{Formula}\quad 14} ) \\{{{vibration}\quad {speed}\quad {2\lbrack n\rbrack}} = {\frac{2\pi \quad V_{rpm}}{60}\frac{2}{\sqrt{3}}\sqrt{| {{{DAT}\lbrack n\rbrack}^{2} - {{{DAT}\lbrack n\rbrack}{{DAT}\lbrack {n + 2} \rbrack}} + {{DAT}\lbrack {n + 2} \rbrack}^{2}} |}}} & ( {{Formula}\quad 15} )\end{matrix}$

[0044] According to claim 13 of the present invention, in theinformation disc recording/playback apparatus defined in claim 12, thecontrol means determines a maximum rotation speed that is lower than theallowable amplitude of the information disc recording/playbackapparatus, on the basis of a value in proportion to an average of twelvevibration speeds 1 or vibration speeds 2 which are calculated for n=0˜5according to (Formula 14) and (Formula 15), respectively, and the trackpitch, or a value in proportion to an average of m pieces of centralvalues selected from the values of the twelve vibration speeds 1 orvibration speeds 2, and the track pitch, or a value in proportion to anaverage of m pieces of central values selected from the second powers ofthe twelve vibration speeds 1 or the second powers of the vibrationspeeds 2, and the track pitch.

[0045] According to claim 14 of the present invention, in theinformation disc recording/playback apparatus defined in claim 7, therotation angle detection means divides the rotation angle information ofthe disc rotation means into six areas for one rotation, and outputs thedivided rotation angle information; and when a difference between thetrack cross amount which is measured at the first rotation speed foreach of the six-divided rotation angles, and the track cross amountwhich is measured with the at least one rotation speed higher than thefirst rotation speed is represented by

[0046] DAT[n]=DAT[0],DAT[1],DAT[2],DAT[3],DAT[4],DAT[5]

[0047] (when n>5, n=n mod 6 (a remainder of n being divided by 6), andthe rotation speed of the disc rotation means is Vrpm[rpm], the controlmeans determines a maximum rotation speed that is lower than theallowable amplitude of the information disc recording/playbackapparatus, on the basis of a value in proportion to a vibrationacceleration 1 or a vibration acceleration 2, or a value in proportionto the second power of the vibration acceleration 1 or the second powerof the vibration acceleration 2, and the track pitch, the vibrationaccelerations 1 and 2 being represented by $\begin{matrix}{{{vibration}\quad {acceleration}\quad {1\lbrack n\rbrack}} = {( \frac{2\pi \quad V_{rpm}}{60} )^{2}\quad \frac{2}{\sqrt{3}}\quad \sqrt{| {{{DAT}\lbrack n\rbrack}^{2} + {{{DAT}\lbrack n\rbrack}{{DAT}\lbrack {n + 1} \rbrack}} + {{DAT}\lbrack {n + 1} \rbrack}^{2}} |}}} & ( {{Formula}\quad 16} ) \\{{{vibration}\quad {acceleration}\quad {2\lbrack n\rbrack}} = {( \frac{2\pi \quad V_{rpm}}{60} )^{2}\frac{2}{\sqrt{3}}\sqrt{| {{{DAT}\lbrack n\rbrack}^{2} - {{{DAT}\lbrack n\rbrack}{{DAT}\lbrack {n + 2} \rbrack}} + {{DAT}\lbrack {n + 2} \rbrack}^{2}} |}}} & ( {{Formula}\quad 17} )\end{matrix}$

[0048] According to claim 15 of the present invention, in theinformation disc recording/playback apparatus defined in claim 14, thecontrol means determines a maximum rotation speed that is lower than theallowable amplitude of the information disc recording/playbackapparatus, on the basis of a value in proportion to an average of twelvevibration accelerations 1 or vibration accelerations 2 which arecalculated for n=0˜5 according to (Formula 16) and (Formula 17),respectively, and the track pitch, or a value in proportion to anaverage of m pieces of central values selected from the values of thetwelve vibration accelerations 1 or vibration accelerations 2, and thetrack pitch, or a value in proportion to an average of m pieces ofcentral values selected from the second powers of the twelve vibrationaccelerations 1 or the second powers of the twelve vibrationaccelerations 2, and the track pitch.

[0049] According to claim 16 of the present invention, in theinformation disc recording/playback apparatus defined in claim 1, thetrack pitch detection means detects the type of the loaded informationdisc, and selects a track pitch corresponding to the detected disc type,with reference to a table in which standard track pitches correspondingto the respective types of the information discs are described.

[0050] According to claim 17 of the present invention, the informationdisc recording/playback apparatus as defined in claim 1 furthercomprises: a move distance detection means for detecting the distance bywhich the reading means moves; and the track pitch detection means formaking the reading means move for a predetermined period of time or by apredetermined distance when the information disc is loaded, counting thenumber of tracks the reading means crosses while it is moving, anddetecting the track pitch on the basis of the move distance and thetrack cross count.

[0051] According to claim 18 of the present invention, the informationrecording/playback apparatus defined in claim 1 further comprises: alinear speed detection means for detecting the linear speed of theinformation disc; a a playback speed detection means for detecting thecurrent playback speed of the information disc; and the track pitchdetection means for calculating the track pitch of the information disc,on the basis of the detected type of the information disc, the linearspeed of the information disc detected by the linear speed detectionmeans, the playback speed detected at a predetermined rotation speed anda predetermined address, the predetermined rotation speed, thepredetermined address, the innermost radius of data area which is uniqueto the detected type of the disc, and the data rate when the disc isplayed at the predetermined playback speed which is unique to the typeof the disc.

[0052] According to claim 19 of the present invention, there is providedan information disc recording/playback apparatus capable of recording orplaying an information disc on which information recording tracks areformed spirally or concentrically, which apparatus comprises: a discrotation means for rotating the information disc at a predeterminedspeed; a reading means for reading an information signal from the disc;a drive means for driving the reading means in the direction of theradius of the disc; a track cross detection means for generating trackcross pulses on the basis of playback signals that are generated whenthe reading means crosses the information tracks; a variable filtermeans for preventing counting of pulses whose widths are narrower than aset value, among the track cross pulses; a count means for counting thepulses outputted from the variable filter means; and a control means fordetermining a maximum rotation speed that is lower than an allowablenumber of track crosses of the information disc recording/playbackapparatus on the basis of the count, or determining a maximum rotationspeed that is lower than an allowable track cross speed or track crossacceleration of the information disc recording/playback apparatus on thebasis of the count and the current disc rotation speed, and controllingthe disc rotation means so that the disc rotation means rotates theinformation disc at a speed lower than the allowable maximum rotationspeed to record or reproduce data in/from the disc.

[0053] According to claim 20 of the present invention, the informationdisc recording/playback apparatus defined in claim 19, furthercomprises: a track cross direction detection means for detecting thetrack cross direction which indicates the direction in which the readingmeans crosses the information tracks; a rotation angle detection meansfor outputting rotation angle information of the disc rotation means;and the count means for counting the track cross pulses with signs,which are detected by the track cross detection means, on the basis ofthe result of the detection by the track cross direction detection meansand the rotation angle information outputted from the rotation angledetection means.

[0054] According to claim 21 of the present invention, there is providedan information disc recording/playback apparatus capable of recording orplaying an information disc on which information recording tracks areformed spirally or concentrically, which apparatus comprises: a discrotation means for rotating the information disc at a predeterminedspeed; a reading means for reading an information signal from the disc;a drive means for driving the reading means in the direction of theradius of the disc; a track cross detection means for generating trackcross pulses on the basis of playback signals that are generated whenthe reading means crosses the information tracks; a variable filtermeans for preventing counting of pulses whose widths are narrower than aset value, among the track cross pulses; a track cross directiondetection means for detecting the track cross direction which indicatesthe direction in which the reading means crosses the information tracks;a rotation angle detection means for outputting rotation angleinformation of the disc rotation means; a count means including a firstcount means for counting the track cross pulses with signs, which areoutputted from the filter means, on the basis of the result of thedetection by the track cross direction detection means and the rotationangle information outputted from the rotation angle detection means, anda second count means for counting the track cross pulses outputted fromthe filter means, without detecting the track cross direction, on thebasis of the rotation angle information outputted from the rotationangle detection means, which count means obtains the count of the firstor second count means when an initial value of count is set for settingan initial value of the variable filter means, a value of the variablefilter is set on the basis of the count and the current rotation speed,the drive means is disabled, and the information disc loaded on the discrotation means is rotated at a predetermined rotation speed, and repeatsthe process of obtaining the count of the first or second count meanswhen the value of the variable filter is set and the information disc isrotated at the predetermined speed, for a required number of times,thereby obtaining the counts for more than one rotation; and a controlmeans for determining a maximum rotation speed that is lower than anallowable number of track crosses of the information discrecording/playback apparatus on the basis of the count, or determining amaximum rotation speed that is lower than an allowable track cross speedor track cross acceleration of the information disc recording/playbackapparatus on the basis of the count and the current disc rotation speed,and controlling the disc rotation means so that the disc rotation meansrotates the information disc at a speed lower than the allowable maximumrotation speed to record or reproduce data in/from the disc.

[0055] According to claim 22 of the present invention, in theinformation disc recording/playback apparatus defined in claim 21, thecount means obtains the count of the first count means when the value ofthe variable filter is set on the basis of the count and the currentrotation speed, the drive means is disabled, and the information discloaded on the disc rotation means is rotated at a predetermined rotationspeed, and repeats the process of obtaining the count of the first countmeans when the information disc is rotated at the predetermined speed,for a required number of times, thereby obtaining the counts for morethan one rotation.

[0056] According to claim 23 of the present invention, in theinformation disc recording/playback apparatus defined in claim 21 or 22,when setting the value of the variable filter on the basis of the countand the current rotation speed, if the count is one obtained withoutdetecting the track cross direction,

[0057] assuming that the total number of track crosses per rotation is4Tc, and the current rotation speed is Vrpm,

[0058] a maximum track cross speed is calculated by $\begin{matrix}{{{maximum}\quad {track}\quad {cross}\quad {speed}} = {\frac{2\pi \quad V_{rpm}}{60}T_{c}}} & ( {{Formula}\quad 18} )\end{matrix}$

[0059] and, on the basis of the calculated maximum track cross speed,the value of the variable filter is set, and a minimum track count pulsewidth is set.

[0060] According to claim 24 of the present invention, in theinformation disc recording/playback apparatus defined in claim 21 or 22,the rotation angle detection means divides the rotation angleinformation of the disc rotation means into six areas for one rotationand outputs the divided rotation angle information, and

[0061] when the count is one obtained when the track cross direction isdetected, the count at each of the six-divided rotation angles isrepresented by

[0062] DAT[n]=DAT[0],DAT[1],DAT[2],DAT[3],DAT[4],DAT[5]

[0063] (when n>5, n=n mod 6 (a remainder of n being divided by 6), and

[0064] the rotation speed of the disc rotation means is Vrpm[rpm],

[0065] a value in proportion to a maximum track cross speed 1 or amaximum track cross speed 2 which are represented as follows arecalculated as a maximum track cross speed, $\begin{matrix}{{{maximum}\quad {track}\quad {cross}\quad {speed}\quad {1\lbrack n\rbrack}} = {\frac{2\pi \quad V_{rpm}}{60}\quad \frac{2}{\sqrt{3}}\quad \sqrt{| {{{DAT}\lbrack n\rbrack}^{2} + {{{DAT}\lbrack n\rbrack}{{DAT}\lbrack {n + 1} \rbrack}} + {{DAT}\lbrack {n + 1} \rbrack}^{2}} |}}} & ( {{Formula}\quad 19} ) \\{{{maximum}\quad {track}\quad {cross}\quad {speed}\quad {2\lbrack n\rbrack}} = {\frac{2\pi \quad V_{rpm}}{60}\frac{2}{\sqrt{3}}\sqrt{| {{{DAT}\lbrack n\rbrack}^{2} - {{{DAT}\lbrack n\rbrack}{{DAT}\lbrack {n + 2} \rbrack}} + {{DAT}\lbrack {n + 2} \rbrack}^{2}} |}}} & ( {{Formula}\quad 20} )\end{matrix}$

[0066] and a value in proportion to an average of twelve maximum trackcross speeds 1 or maximum track cross speeds 2 which are calculated forn=0˜5 according to (Formula 19) and (Formula 20), respectively, or avalue in proportion to an average of m pieces of central values selectedfrom the values of the twelve maximum track cross speeds 1 or maximumtrack cross speeds 2, is employed as a maximum track cross speed.

[0067] According to claim 25 of the present invention, in theinformation disc recording/playback apparatus defined in claim 24, whenthe value of the variable filter is set on the basis of the count andthe current rotation speed, if the count is one obtained when the trackcross direction is detected, the count at each of the six-dividedrotation angles is represented by

[0068] DAT[n]=DAT[0],DAT[1],DAT[2],DAT[3],DAT[4],DAT[5]

[0069] (when n>5, n=n mod 6 (a remainder of n being divided by 6), and

[0070] the rotation speed of the disc rotation means is Vrpm[rpm],

[0071] a maximum track cross speed is calculated on the basis of thefollowing formulae,

4T _(C) =|DAT[0]|+|DAT[1]|+|DAT[2]|+|DAT[3]|+|DAT[4]|+|DAT[5]|  (Formula21)

[0072] $\begin{matrix}{{{maximum}\quad {track}\quad {cross}\quad {speed}} = {{\frac{2\pi \quad V_{rpm}}{60}T_{c}\frac{1}{\cos \frac{\pi}{6}}} = {\frac{2\pi \quad V_{rpm}}{60}T_{c}\frac{2}{\sqrt{3}}}}} & ( {{Formula}\quad 22} )\end{matrix}$

[0073] and, on the basis of the maximum track cross speed so calculated,the value of the variable filter is set, and a minimum track count pulsewidth is set.

[0074] According to claim 26 of the present invention, in theinformation disc recording/playback apparatus defined in claim 19, whensetting the maximum rotation speed of the information discrecording/playback apparatus, the control means employs, as the count, adifference between the track cross count that is obtained when theinformation disc is rotated at a first rotation speed and at least onerotation speed that is higher than the first rotation speed, and thecount obtained with the at least one rotation speed that is higher thanthe first rotation speed.

[0075] According to claim 27 of the present invention, in theinformation disc recording/playback apparatus defined in claim 19, thetrack cross count is the number of track crosses which is calculated onthe basis of an average of counts corresponding to more than onerotation, which counts are selected from among the counts obtained bythe repetition.

[0076] According to claim 28 of the present invention, in theinformation disc recording/playback apparatus defined in claim 27, whencalculating the track cross count, if the value of the variable filtermeans which is reset by repetition at the same rotation speed changes bya predetermined value or more, the counts obtained before the change arenot used as the counts for calculating the average.

[0077] According to claim 29 of the present invention, there is providedan information disc recording/playback apparatus capable of recording orplaying an information disc on which information recording tracks areformed spirally or concentrically, which apparatus comprises: a discrotation means for rotating the information disc at a predeterminedspeed; a reading means for reading an information signal from the disc;a drive means for driving the reading means in the direction of theradius of the disc; a track cross detection means for generating trackcross signals on the basis of playback signals that are generated whenthe reading means crosses the information tracks; a pulse width storagemeans for holding the pulse width of a just-previous track cross signal;a filter means for comparing the pulse width of the just-previous trackcross signal with the pulse width of the current track cross signal, andpreventing the current track cross signal from being outputted when thecurrent track cross signal is reduced by a predetermined value or more;a count means for counting the pulses which are outputted from thevariable filter means; and a control means for determining a maximumrotation speed that is lower than an allowable number of track crossesof the information disc recording/playback apparatus on the basis of theobtained counts for one or more rotation, or determining a maximumrotation speed that is lower than an allowable track cross speed ortrack cross acceleration of the information disc recording/playbackapparatus on the basis of the obtained counts for one or more rotation,and the current disc rotation speed, and controlling the disc rotationmeans so that the disc rotation means rotates the information disc at aspeed lower than the allowable maximum rotation speed to record orreproduce data in/from the disc.

[0078] According to claim 30 of the present invention, in theinformation disc recording/playback apparatus defined in claim 29, theinformation disc recording/playback apparatus is able to record or playtwo or more kinds of information discs having different track pitches;and setting of the maximum rotation speed of the information discrecording/playback apparatus is performed by detecting the track pitchof the information disc, and determining a maximum rotation speed thatis lower than an allowable vibration amplitude of the information discrecording/playback apparatus on the basis of the count and the trackpitch, or determining a maximum rotation speed that is lower than anallowable vibration speed or vibration acceleration of the informationdisc recording/playback apparatus on the basis of the count, the trackpitch, and the current disc rotation speed.

[0079] According to claim 31 of the present invention, there is provideda vibration detection method for an information disc recording/playbackapparatus capable of recording or playing at least two kinds ofinformation discs having different track pitches, on which informationrecording tracks are formed spirally or concentrically, which methodcomprises: a step of detecting the track pitch of the information disc;a step of counting track cross pulses on the basis of playback signalswhich are generated when the information disc fixedly loaded on theapparatus is rotated and a reading unit crosses the information trackson the information disc, thereby obtaining a count; a step ofdetermining a maximum rotation speed that is lower than an allowablevibration amplitude of the information disc recording/playbackapparatus, on the basis of the obtained count and the track pitch; and astep of determining a maximum rotation speed that is lower than anallowable vibration speed or vibration acceleration of the informationdisc recording/playback apparatus, on the basis of the count, the trackpitch, and the current disc rotation speed.

[0080] According to claim 32 of the present invention, there is provideda vibration detection method for an information disc recording/playbackapparatus capable of recording or playing at least two kinds ofinformation discs having different track pitches, on which informationrecording tracks are formed spirally or concentrically, which methodcomprises: a step of detecting the track pitch of the information disc;a step of detecting the track cross direction indicating the directionin which a reading means crosses the information tracks; a step ofoutputting rotation angle information of the information disc, which isdivided into n areas for one rotation; a step of detecting two areaswherein the track cross speed has the lowest value, from among then-divided areas; a step of counting track cross pulses, which are basedon playback signals that are generated when the information disc fixedlyloaded onto the apparatus is rotated and the reading means crosses theinformation tracks on the information disc, such that the track crosspulses with signs are counted while detecting the track cross directionin an area where the track cross speed has the lowest value, on thebasis of the detected track cross direction and the rotation angleinformation; a step of counting track cross pulses, which are based onplayback signals that are generated when the information disc fixedlyloaded onto the apparatus is rotated and the reading means crosses theinformation tracks on the information disc, such that the track crosspulses with signs are counted without detecting the track crossdirection, on the basis of the track cross direction which has justpreviously been detected, in an area where the track cross speed doesnot have the lowest value; a step of determining a maximum rotationspeed that is lower than an allowable vibration amplitude of theinformation disc recording/playback apparatus, on the basis of theobtained count and the track pitch; and a step of determining a maximumrotation speed that is lower than an allowable vibration speed orvibration acceleration of the information disc recording/playbackapparatus, on the basis of the count, the track pitch, and the currentdisc rotation speed.

[0081] According to claim 33 of the present invention, there is provideda vibration detection method for an information disc recording/playbackapparatus capable of recording or playing at least two kinds ofinformation discs having different track pitches, on which informationrecording tracks are formed spirally or concentrically, which methodcomprises: a step of detecting the track pitch of the information disc;a step of detecting the track cross direction indicating the directionin which a reading means crosses the information tracks; a step ofoutputting rotation angle information of the information disc, which isdivided into n areas for one rotation; a step of detecting two areaswherein the track cross speed has the lowest value, from among then-divided areas; a step of obtaining a first count on the basis ofplayback signals which are generated when the information disc fixedlyloaded onto the apparatus is rotated and the reading means crosses theinformation tracks on the information disc; a step of obtaining a secondcount in which a sign is added to the count, on the basis of the trackcross direction which has just previously been detected, when theinformation disc is rotated; a step of selecting the first count in anarea where the track cross speed has the lowest value, and selecting thesecond count in an area where the track cross speed does not have thelowest value, thereby counting the track cross pulses for every rotationangle and outputting the count; a step of determining a maximum rotationspeed that is lower than an allowable vibration amplitude of theinformation disc recording/playback apparatus, on the basis of theobtained count and the track pitch; and a step of determining a maximumrotation speed that is lower than an allowable vibration speed orvibration acceleration of the information disc recording/playbackapparatus, on the basis of the count, the track pitch, and the currentdisc rotation speed.

[0082] According to claim 34 of the present invention, there is provideda vibration detection method for an information disc recording/playbackapparatus capable of recording or playing at least two kinds ofinformation discs having different track pitches, on which informationrecording tracks are formed spirally or concentrically, which methodcomprises: a step of detecting the track pitch of the information disc;a step of counting track cross pulses on the basis of playback signalswhich are generated when the information disc fixedly loaded onto theapparatus is rotated at a first rotation speed and a reading unitcrosses the information tracks on the information disc, therebyobtaining a count; a step of calculating a difference between a trackcross count which is obtained when the information disc is rotated withat least one rotation speed that is higher than the first rotationspeed, and a count which is obtained when the information disc isrotated at the first rotation speed, thereby obtaining a differencecount; a step of determining a maximum rotation speed that is lower thanan allowable vibration amplitude of the information discrecording/playback apparatus, on the basis of the obtained differencecount and the track pitch; and a step of determining a maximum rotationspeed that is lower than an allowable vibration speed or vibrationacceleration of the information disc recording/playback apparatus, onthe basis of the difference count, the track pitch, and the current discrotation speed.

[0083] According to claim 35 of the present invention, there is provideda vibration detection method for an information disc recording/playbackapparatus capable of recording or playing an information disc on whichinformation recording tracks are formed spirally or concentrically,which method comprises: a step of counting track cross pulses on thebasis of playback signals which are generated when the information discfixedly loaded on the apparatus is rotated and a reading unit crossesthe information tracks on the information disc, thereby obtaining acount; a step of comparing the widths of the detected track pulses witha predetermined value, and invalidating the counts of track pulses whosewidths are shorter than the predetermined value; a step of determining amaximum rotation speed that is lower than an allowable number of trackcrosses of the information disc recording/playback apparatus, on thebasis of the count; and a step of determining a maximum rotation speedthat is lower than an allowable track cross speed or track crossacceleration, on the basis of the count and the current disc rotationspeed.

[0084] According to claim 36 of the present invention, there is provideda vibration detection method for an information disc recording/playbackapparatus capable of recording or playing an information disc on whichinformation recording tracks are formed spirally or concentrically,which method comprises: a step of counting track cross pulses on thebasis of playback signals which are generated when the information discfixedly loaded on the apparatus is rotated and a reading unit crossesthe information tracks on the information disc, thereby obtaining acount; a step of detecting the track cross direction indicating thedirection in which the reading means crosses the information tracks; astep of outputting rotation angle information of the information disc; astep of comparing a set pulse width with the pulse width of the currenttrack cross pulse, and invalidating the count of the current track crosspulse when its pulse width is decreased by a predetermined value ormore; a first count step of counting the track cross pulses with signs,whose widths are not decreased by the predetermined value or more, onthe basis of the track cross direction and the rotation angleinformation; a second count step of counting the track cross pulseswhose widths are not decreased by the predetermined value or more,without detecting the track cross direction, on the basis of therotation angle information; a step of setting the set pulse widths byrepeating the steps of obtaining the first and second counts by arequired number of times; a step of obtaining a count corresponding toone or more rotation of the information disc, by obtaining the countsobtained in the first and second count steps using the repeatedly setpulse widths; a step of determining a maximum rotation speed that islower than an allowable number of track crosses of the information discrecording/playback apparatus, on the basis of the count; and a step ofdetermining a maximum rotation speed that is lower than an allowabletrack cross speed or track cross acceleration, on the basis of the countand the current disc rotation speed.

[0085] According to claim 37 of the present invention, there is provideda vibration detection method for an information disc recording/playbackapparatus capable of recording or playing an information disc on whichinformation recording tracks are formed spirally or concentrically,which method comprises: a step of counting track cross pulses on thebasis of playback signals which are generated when the information discfixedly loaded on the apparatus is rotated and a reading unit crossesthe information tracks on the information disc, thereby obtaining acount; a step of storing the pulse width of a track cross pulse whichhas just previously been detected; a step of comparing the stored trackcross pulse width with the pulse width of the current track cross pulse,and invalidating the count of the current track cross pulse when itspulse width is decreased by a predetermined value or more; a step ofdetermining a maximum rotation speed that is lower than an allowablenumber of track crosses of the information disc recording/playbackapparatus, on the basis of the count; and a step of determining amaximum rotation speed that is lower than an allowable track cross speedor track cross acceleration, on the basis of the count and the currentdisc rotation speed.

[0086] As described above, according to an information discrecording/playback apparatus and a vibration detection method for theinformation disc recording/playback apparatus relating to the presentinvention, there is provided an information disc recording/playbackapparatus capable of recording or playing at least two kinds ofinformation discs having different track pitches, on which informationrecording tracks are formed spirally or concentrically, which apparatuscomprises: a disc rotation means for rotating the information disc at apredetermined speed; a reading means for reading an information signalfrom the disc; a drive means for driving the reading means in thedirection of the radius of the disc; a track pitch detection means fordetecting the track pitch of the information disc from the informationdisc; a track cross detection means for generating track cross signalson the basis of playback signals that are generated when the readingmeans crosses the information tracks; a count means for counting trackcross pulses that are detected by the track cross detection means, andoutputting the count; and a control means for determining a maximumrotation speed that is lower than an allowable vibration amplitude ofthe information disc recording/playback apparatus on the basis of thecount and the track pitch, or determining a maximum rotation speed thatis lower than an allowable vibration speed or vibration accelerationspeed of the information disc recording/playback apparatus on the basisof the count, the track pitch, and the current disc rotation speed, andcontrolling the disc rotation means so that the disc rotation meansrotates the information disc at a speed lower than the allowable maximumrotation speed to record or reproduce data in/from the disc. Therefore,the vibration amplitude, or vibration speed, or vibration accelerationis evaluated considering the track pitch of the disc, and the maximumrotation speed lower than the allowable vibration amplitude, orvibration speed, or vibration acceleration of the information discrecording/playback apparatus is determined, whereby vibration detectioncan be carried out using a single threshold value, regardless of thetype of the information disc.

[0087] Furthermore, according to an information disc recording/playbackapparatus and a vibration detection method for the information discrecording/playback apparatus relating to the present invention, there isprovided an information disc recording/playback apparatus capable ofrecording or playing an information disc on which information recordingtracks are formed spirally or concentrically, which apparatus comprises:a disc rotation means for rotating the information disc at apredetermined speed; a reading means for reading an information signalfrom the disc; a drive means for driving the reading means in thedirection of the radius of the disc; a track cross detection means forgenerating track cross pulses on the basis of playback signals that aregenerated when the reading means crosses the information tracks; avariable filter means for preventing counting of pulses whose widths arenarrower than a set value, among the track cross pulses; a count meansfor counting the pulses outputted from the variable filter means; and acontrol means for determining a maximum rotation speed that is lowerthan an allowable number of track crosses of the information discrecording/playback apparatus on the basis of the count, or determining amaximum rotation speed that is lower than an allowable track cross speedor track cross acceleration of the information disc recording/playbackapparatus on the basis of the count and the current disc rotation speed,and controlling the disc rotation means so that the disc rotation meansrotates the information disc at a speed lower than the allowable maximumrotation speed to record or reproduce data in/from the disc. Sincesetting of the track cross filter is carried out on the basis of thetrack cross count and the current rotation speed, even when the trackcross speed varies significantly due to the eccentricity or vibration ofthe disc, track counting most suitable for vibration detection can beaccurately carried out at all times.

[0088] Furthermore, according to an information disc recording/playbackapparatus relating to the present invention, there is provided aninformation disc recording/playback apparatus capable of recording orplaying an information disc on which information recording tracks areformed spirally or concentrically, which apparatus comprises: a discrotation means for rotating the information disc at a predeterminedspeed; a reading means for reading an information signal from the disc;a drive means for driving the reading means in the direction of theradius of the disc; a track cross detection means for generating trackcross signals on the basis of playback signals that are generated whenthe reading means crosses the information tracks; a pulse width storagemeans for holding the pulse width of a just-previous track cross signal;a filter means for comparing the pulse width of the just-previous trackcross signal with the pulse width of the current track cross signal, andpreventing the current track cross signal from being outputted when thecurrent track cross signal is reduced by a predetermined value or more;a count means for counting the pulses which are outputted from thevariable filter means; and a control means for determining a maximumrotation speed that is lower than an allowable number of track crossesof the information disc recording/playback apparatus on the basis of theobtained counts for one or more rotation, or determining a maximumrotation speed that is lower than an allowable track cross speed ortrack cross acceleration of the information disc recording/playbackapparatus on the basis of the obtained counts for one or more rotation,and the current disc rotation speed, and controlling the disc rotationmeans so that the disc rotation means rotates the information disc at aspeed lower than the allowable maximum rotation speed to record orreproduce data in/from the disc. Therefore, when the current pulse widthis smaller than the previous pulse width by a predetermined value, thispulse is judged as one caused by false detection due to noise and is notcounted, whereby track counting most suitable for vibration detectioncan be accurately carried out at all times, without requiring time forexcess measurement.

BRIEF DESCRIPTION OF THE DRAWINGS

[0089]FIG. 1 is a block diagram illustrating the construction of aDVD-ROM player in the case where an information disc recording/playbackapparatus and a vibration detection method for the information discrecording/playback apparatus according to a first or fourth embodimentof the invention are applied to the DVD-ROM player.

[0090]FIG. 2 is a block diagram illustrating the construction of aDVD-ROM player in the case where an information disc recording/playbackapparatus and a vibration detection method for the information discrecording/playback apparatus according to a second embodiment of theinvention are applied to the DVD-ROM player.

[0091]FIG. 3 is a block diagram illustrating the construction of aDVD-ROM player in the case where an information disc recording/playbackapparatus and a vibration detection method for the information discrecording/playback apparatus according to a third embodiment of theinvention are applied to the DVD-ROM player.

[0092]FIG. 4 is a block diagram illustrating the construction of aDVD-ROM player in the case where an information disc recording/playbackapparatus and a vibration detection method for the information discrecording/playback apparatus according to a fifth embodiment of theinvention are applied to the DVD-ROM player.

[0093]FIG. 5 is a block diagram illustrating the construction of aDVD-ROM player in the case where an information disc recording/playbackapparatus and a vibration detection method for the information discrecording/playback apparatus according to a sixth, seventh, or eighthembodiment of the invention are applied to the DVD-ROM player.

[0094]FIG. 6 is a diagram illustrating a graph showing the amount ofdisplacement of the count at every rotation angle, which displacement iscaused by vibration or eccentricity, when the present invention isapplied to the DVD-ROM player.

[0095]FIG. 7 is a block diagram illustrating the construction of aDVD-ROM player in the case where an information disc recording/playbackapparatus and a vibration detection method for the information discrecording/playback apparatus according to a ninth embodiment of theinvention are applied to the DVD-ROM player.

[0096]FIG. 8 is a block diagram illustrating the construction of aconventional optical disc playback apparatus which performs vibrationdetection using an acceleration sensor.

[0097]FIG. 9 is a block diagram illustrating the construction of aconventional optical disc playback apparatus which performs vibrationdetection using track counting.

[0098]FIG. 10 is a block diagram illustrating the construction ofanother DVD-ROM player in the case where an information discrecording/playback apparatus and a vibration detection method for theinformation disc recording/playback apparatus according to the fifthembodiment of the invention are applied to the DVD-ROM player.

BEST MODE TO EXECUTE THE INVENTION

[0099] (Embodiment 1)

[0100] An information disc recording/playback apparatus and a vibrationdetection method for the information disc recording/playback apparatusaccording to a first embodiment of the present invention will bedescribed taking a DVD-ROM player as an example, with reference to FIG.1.

[0101] In FIG. 1, a DVD-ROM player 101 is able to play various kinds ofoptical discs 102. The DVD-ROM player 101 according to this firstembodiment is able to play the following discs: CD-ROM (CD-ROM, CD-R,CD-RW), DVD-ROM (DVD-5, DVD-9, DVD-R4.7G), and DVD-R3.9G, and thestandard track pitches of these discs are as follows: CD-ROM  1.6 μmDVD-ROM 0.74 μm DVD-R3.9G 0.80 μm

[0102] Reference numeral 103 denotes a disc rotation means for rotatingthe optical disc 102 mounted on the DVD-ROM player 101 at apredetermined rpm. Reference numeral 104 denotes a reading means forreading an information signal from the optical disc 102. In the DVD-ROMplayer 101, the reading means 104 comprises, for example, a laseremission element 105 for emitting two laser beams having differentoscillation wavelengths, one for a CD-ROM and the other for a DVD-ROM;an objective lens 106 for converging the laser beams; and a two-elementphotodetector 107, one for a CD-ROM and the other for a DVD-ROM. Thereading means 104 amplifies the outputs from the photodetector 107,selects one of the output signals from the photodetector 107 accordingto the type of the optical disc 102, generates a tracking error (TE)signal, a focus error (FE) signal, a playback signal (RF), an All Sumsignal (AS), an RF envelope signal (RFENV) and the like, and outputsthese signals.

[0103] Reference numeral 108 denotes a conversion means for convertingthe playback signal outputted from the reading means 104 into digitaldata. Reference numeral 109 denotes a drive means for driving thereading means 104 in the direction of the radius of the optical disc102. This drive means 109 comprises, for example, a traverse drive means110 for driving the whole reading means 104 in the direction of theradius of the optical disc, and a tracking actuator 111 for minutelydriving the objective lens 106 included in the reading means 104, in thedirection of the radius of the optical disc.

[0104] Reference numeral 112 denotes a track cross detection means forgenerating track cross pulses on the basis of playback signals which aregenerated when the laser beam outputted from the reading means 104crosses the tracks on the optical disc 102. Reference numeral 113denotes a track cross direction detection means for detecting thedirection along which the laser beam from the reading means 104 crossesthe tracks on the optical disc. The track cross detection means 112 orthe track cross direction detection means 113 binarizes the trackingerror signal outputted from the reading means 104 with a hysteresiscomparator or a comparator to generate a track count signal TKC.Likewise, the track cross detection means 112 or the track crossdirection detection means 113 generates a non-on track signal OFTR fromthe envelope of the RF signal, and generates a track cross directionsignal according to the phase relationship between the TKC and the OFTR,or generates a track cross detection pulse by directly using the TKC orby latching the TKC with the OFTR.

[0105] Reference numeral 114 denotes a rotation angle detection meansfor detecting the rotation angle of the disc rotation means 103. Therotation angle detection means 114 generally utilizes a signal called anFG pulse that is generated from the output of a Hall element of a discmotor. As the FG signal outputs three pulses for one rotation with athree-phase motor, rotation angle detection in units of 60 degrees ispossible by counting both of a rising edge and a falling edge. Further,there are proposed a method of performing more accurate rotation angledetection by frequency-dividing the FG pulse, and a method of detectingthe rotation speed at an arbitrarily resolution by providing the discmotor with a rotation speed detection means using an encoder.

[0106] Reference numeral 115 denotes a count means for counting thenumber of track crosses including the direction, on the basis of theoutput from the rotation angle detection means 105, and the outputs fromthe track cross detection means 112 and the track cross directiondetection means 113. In the above-mentioned case where the rotationangle can be detected at every 60 degrees, one rotation is divided intosix areas, and a signed track count is obtained for each area.

[0107] Reference numeral 116 denotes a control means for processing thesignals supplied from the conversion means 108 and the count means 115,and controlling the disc rotation means 103, the reading means 104, theconversion means 108, and the drive means 109.

[0108] Next, the operation will be described. Initially, a descriptionwill be given of a step in which the control means 116 sets a maximumrotation speed of the DVD-ROM player.

[0109] A step of detecting the track pitch of the optical disc 102 willbe described taking, for example, a method of determining the type ofthe information disc and selecting a standard track pitch according tothe information about the disc type. Usually, the DVD-ROM player 101 canplay plural types of information discs as described above, and therequired light source and the method for generating a detection signalvary among the plural disc types. Therefore, initially, the type of theloaded disc is determined by various methods. For example, the loadedinformation disc is discriminated between a ROM (CD-ROM/R, DVD-ROM/R)disc and a rewritable disc (CD-RW), from the reflectivity of theinformation disc, using a CD laser, on the basis of the amplitude of afocus error signal obtained in focus search, and furthermore, it isdiscriminated between a DVD disc and a CD disc, from the degree ofmodulation of an RF signal, and thereafter, required light source andsignal path are selected. Finally, it is checked whether TOC (TABLE OFCONTENTS) information can be read from the disc or not, and further, itis checked whether the disc type selected from the contents of the TOCinformation is correct or not. Then, the standard value of the trackpitch according to the disc type is selected.

[0110] In a step of obtaining the result of counting by the count meanswhen the disc is rotated at the first rotation speed, the drive means104 is disabled, and the optical disc 102 is rotated at the firstrotation speed by controlling the disc rotation means 103. Then, theresult of counting by the count means 115 is captured. In this firstembodiment, using a three-phase motor, utilizing an FG signal outputtedfrom a Hall element, the rotation angle is detected at the rising andfalling edges of the FG signal, and the counted number of track crossesis obtained at every rotation angle of 60 degrees. Further, in thisfirst embodiment, the first rotation speed is set at a sufficiently lowspeed which does not cause vibration between the reading means 104 andthe optical disc 102, and the number of track crosses caused by only theeccentricity between the optical disc 102 and the disc rotation means103 is measured.

[0111] Also in a step of obtaining the count of the count means when theoptical disc 102 is rotated with at least one rotation speed that ishigher than the first rotation speed, the number of track crosses can becounted at every rotation angle of 60 degrees, as in the step ofobtaining the count of the count means when the disc is rotated at thefirst rotation speed. In this first embodiment, the count is obtained atthe maximum rotation speed that is set for every disc type of theDVD-ROM player.

[0112] Next, each of the counts obtained when the disc is rotated at thefirst speed and the at least one speed higher than the first speed ismultiplied by the track pitch which is detected in the track pitchdetection step, thereby obtaining data of the track cross amount. Inthis embodiment, data of the track cross amount at every 60 degrees iscalculated from the number of tracks counted at every rotation angle of60 degrees.

[0113] In a step of calculating the vibration amplitude of the opticaldisc 102 with respect to the reading means 104, the track cross amountdetected at the first rotation speed is compared with the track crossamount detected with the at least one rotation speed higher than thefirst speed, and the vibration amplitude of the information disc withrespect to the reading means is calculated on the basis of a differencebetween the track cross amounts. In this first embodiment, a differencebetween the track cross amount detected at the first rotation speed andthe track cross amount detected at the maximum rotation speed isobtained at every rotation angle of 60 degrees, thereby calculating atrack cross component due to the vibration. Then, the vibrationamplitude is obtained on the assumption that the vibration is asinusoidal wave.

[0114] In a step of determining the maximum rotation speed, comparisonis carried out as to whether the previously obtained vibration amplitudeis lower than a reference value or not. When it is lower than thereference value, the maximum rotation speed that is set for every disctype is employed, and when it is higher than the reference value, arotation speed lower than the maximum rotation speed is employed.

[0115] Then, reproduction of data is carried out at a speed lower thanthe set maximum rotation speed.

[0116] Next, a description will be given of a case where vibration of aCD-ROM is to be detected.

[0117] A CD-ROM disc loaded on the DVD-ROM player 101 is fixed to thedisc rotation means 103. Next, focus search is carried out with a laserbeam for CD-ROM, and the amplitude of a focus error signal is measured.As a result, the loaded CD-ROM disc is judged as a ROM disc because itsreflectivity is relatively high. Next, the CD-ROM disc is rotated at apredetermined speed by the disc rotation means 103, and the degree ofmodulation of an RF signal is measured. The measured degree of amplitudeis compared with a reference value, whereby the CD-ROM disc is judged asa CD disc, whereby the result of disc judgement is a CD-ROM. Also when aDVD-ROM disc is employed, the disc is judged as a DVD-ROM disc in thesame manner as described above, and then it is checked whether theDVD-ROM disc is a DVD-R4.7G (track pitch: 0.74 μm) or a DVD-R3.9G (trackpitch: 0.8 μm) by reading the TOC information, whereby the track pitchcan be detected.

[0118] Next, the CD-ROM disc is rotated at a sufficiently low speed,1200 rpm, which does not cause vibration between the disc and thereading means 104. Then, the traverse drive means 110 and the trackingactuator 111 are disabled, and the count of the count means 115 isobtained at every rotation angle of 60 degrees. Since no vibrationoccurs between the disc and the reading means 104, the count due to onlythe eccentricity component between them is obtained. For example, thecount may be obtained by a method of performing counting for pluralrotations with one rotation as a unit, and averaging the obtainedcounts, or a method of performing counting for plural rotations asdescribed above, and selecting, from the obtained counts, plural countswhich are not supposed to be false counts.

[0119] Next, the CD-ROM disc is rotated at the maximum rotation speed ofthe CD-ROM disc. In this example, the CD-ROM disc is able to perform CAVplayback at 24X(maximum)-speed, 12X-speed, and 6X-speed. Since themaximum rotation speed is 5000 rpm, the 12X-speed is 2500 rpm, and the6X-speed is 1250 rpm, the count when the disc is rotated at 5000 rpm isobtained.

[0120] Next, a difference between the counts obtained at 1200 rpm and5000 rpm for every rotation angle is calculated, whereby the track countdue to the vibration at 5000 rpm, excluding the eccentricity component,is obtained.

[0121] Finally, the vibration amplitude of this disc is evaluated fromthis track count and the track pitch, or the vibration speed orvibration acceleration is evaluated from the track count, the trackpitch, and the rotation speed of 5000 rpm, and it is decided whether thedisc is to be rotated at the maximum rotation speed or not, according towhether the vibration amplitude, or the vibration speed, or thevibration acceleration is lower than the allowable value or not. Forexample, when it is higher than the allowable value, the maximumrotation speed is reduced to 2500 rpm of the 12X-speed.

[0122] As described above, according to the first embodiment, thevibration amount, or vibration speed, or vibration acceleration isevaluated considering the track pitch of the disc, and a maximumrotation speed that is lower than the allowable vibration amplitude, orvibration speed, or vibration acceleration of the information discrecording/playback apparatus is decided. Therefore, vibration detectioncan be carried out using a single threshold value, independently of thetype of the information disc.

[0123] In this first embodiment, counting of the track crosses iscarried out at plural rotation speeds while detecting the rotationangle, and a difference between them is calculated to obtain the trackcount due to vibration. However, there may be employed a method ofsimply counting the track crosses at plural rotation speeds withoutdetecting the rotation angle and then taking a difference between them,or a method of counting the track crosses at a single rotation speedwithout detecting the rotation angle.

[0124] Furthermore, while in this first embodiment evaluation ofvibration is performed on the basis of a difference between the countobtained at a low speed at which no vibration occurs and the countobtained at the maximum rotation speed, it may be performed on the basisof a difference between the count obtained at a rotation speed at whichvibration occurs and the count obtained at the maximum rotation speed.Further, not the maximum rotation speed but a rotation speed lower thanthe maximum rotation speed may be employed. Furthermore, evaluation maybe carried out at two or more rotation speeds, and the playback speedmay be set as follows: the maximum rotation speed, a speed lower thanthe maximum rotation speed, a speed lower than that speed, . . .

[0125] Moreover, in this first embodiment, the counted number of trackcrosses is multiplied by the track pitch to obtain data of the trackcross amount, and the track cross amount due to vibration is calculatedby operating the track cross amount, and the vibration amplitude isobtained on the basis of the track cross amount due to vibration.However, as for the track pitch of the disc, the value of the trackpitch itself may be employed, or the ratio of track pitches of pluraldiscs may be employed. Furthermore, when the number of track crosses dueto vibration is obtained by operating the result of counting, the numberof track crosses may be multiplied by the track pitch to obtain thetrack cross amount due to vibration and, thereafter, the vibrationamplitude may be obtained. Alternatively, the vibration amount with thenumber of track crosses as a unit may be obtained, and the vibrationamount may be multiplied by the track pitch to obtain the vibrationamplitude.

[0126] Furthermore, while in this first embodiment the vibrationamplitude is obtained and compared with a reference value, not thevibration amplitude itself but a value in proportion to the vibrationamplitude or a value in proportion to the second power of the vibrationamplitude may be calculated to be compared with the reference value.Further, the vibration speed or vibration acceleration may be obtainedinstead of the vibration amplitude.

[0127] While in this first embodiment detection of vibration of a CD-ROMdisc is described, vibrations of discs having different track pitches,such as a DVD and a DVD-R3.9G, can be detected in like manner asdescribed above.

[0128] While in this first embodiment a DVD-ROM player capable ofplaying CD-ROM, DVD-ROM, DVD-R3.9G, and DVD-R4.7G is described as anexample, any information disc player may be employed as long as it canplay plural kinds of information discs having different track pitches.

[0129] Furthermore, while in this first embodiment a DVD-ROM player isdescribed as an example, the present invention is applicable to a casewhere a maximum recording speed at recording is set in other writablerecording/playback apparatuses such as CD-R, CD-RW, and DVD-R.

[0130] (Embodiment 2)

[0131] Hereinafter, an information disc recording/playback apparatus anda vibration detection method for the information disc recording/playbackapparatus according to a second embodiment of the present invention willbe described, taking a DVD-ROM player as an example, with reference toFIG. 2.

[0132] In FIG. 2, the same reference numerals as those shown in FIG. 1denote the same or corresponding parts, and reference numeral 201denotes a track cross speed detection means for detecting a track crossspeed on the basis of the output from the track cross detection means112.

[0133] The count means 115 counts the track count pulses while detectingthe direction when the track cross speed is lower than a predeterminedvalue, and counts the track count pulses without detecting the directionwhen the track cross speed is higher than the predetermined value, onthe basis of the output from the track cross speed detection means 201.When it is switched to “without direction detection”, the track crossdirection can be known on the basis of the direction obtained whencounting with direction detection has been most recently carried out.

[0134] The maximum speed at which track counting with directiondetection can be carried out depends on the track counting method or thedisc type.

[0135] For example, when tracking error detection is carried out by thethree-beam method for a CD or by the phase difference method for a DVD,generally the three-beam method is able to perform direction detectionat a higher speed. Accordingly, a threshold value for determining as towhether track counting is to be carried out with direction detection ornot may be set for each disc type, or it may be set adaptively to a discof the lowest speed at which track counting with direction detection ispossible.

[0136] As described above, according to the second embodiment, the trackcross speed detection means 201 is provided, and the track countingmethod is changed by detecting the track cross frequency. Therefore,even when detection of the track cross direction is difficult because ofthe change in the track cross speed, track counting can be performedwith accuracy, whereby accurate vibration detection can be performed atall times.

[0137] (Embodiment 3)

[0138] Hereinafter, an information disc recording/playback apparatus anda vibration detection method for the information disc recording/playbackapparatus according to a third embodiment of the present invention willbe described, taking a DVD-ROM player as an example, with reference toFIGS. 3 and 6.

[0139] In FIG. 3, the same reference numerals as those shown in FIG. 1denote the same or corresponding parts, and reference numeral 301denotes a zero cross area detection means for detecting an area wherethe track cross speed has the lowest value. The rotation angle detectionmeans 114 usually employs a signal called an FG pulse that is generatedfrom the output of a Hall element of a disc motor. Since the FG signaloutputs three pulses for one rotation with a three-phase motor, rotationangle detection in units of 60 degrees can be carried out by countingboth of rising and falling edges. In this third embodiment, adescription will be given of a case where rotation angle detection isperformed in units of 60 degrees using the FG pulses.

[0140] The zero cross area detection means 301 detects two areas eachincluding a position where the track cross speed has the lowest value.For example, there may be employed a method of detecting areas where thetrack cross speed has the lowest value by using the track cross speeddetection means 112, or a method of detecting, as zero cross areas, anarea where the absolute value of the track count has the lowest value,and an area on a diagonal line with respect to the area from among thesix-divided areas.

[0141] Hereinafter, a description will be given of the reason why thearea where the absolute value of the track count has the lowest valueand the area on a diagonal line with respect to this area, among thesix-divided areas, are zero cross areas.

[0142]FIG. 6 is a graph illustrating the amount of displacement of thecount by the count means 115 at every rotation angle, which displacementis caused by vibration or eccentricity. A count DAT[n] in a zero crossarea within a range of φ=0˜60°, which is a signed count obtained whenperforming direction detection, is represented by

DAT[n]=T _(c)cos(φ)−cos(φ−60)  (Formula 23)

[0143] Likewise, counts DAT[n] and DAT[n+1] in two areas which are notzero cross areas, within a range of φ=0˜60°, are represented by

DAT[n+1] T _(c)cos(φ+60)−T _(c)cos(φ)  (Formula 24)

DAT[n+2] T _(c)cos(φ+120)−T _(c)cos(φ+60)  (Formula 25)

[0144] A maximum value of |DAT[n]| within this range is represented bywhen φ=0˜60°,

|DAT[n]|=0.5T _(c)

[0145] Likewise, minimum values of DAT[n+1] and DAT[n+2] are representedby

[0146] when φ=0°,

|DAT[n+1]|=0.5T _(c)

[0147] when φ=60°,

|DAT[n+2]|=0.5T _(c)

[0148] According, the following relationship always holds.

|DAT[n]|≧|DAT[n+1],|DAT[n+2]|

[0149] Likewise, when the count is obtained without performing directiondetection, since only the number of track crosses is counteddisregarding the track cross direction, a count DAT[n] in a zero crossarea, within a range of φ=0˜60°, with cos(0) as a boundary, isrepresented by

DAT[n]=|T _(c)(cos(0)−cos(φ)) |+|T _(χ)(cos(φ−60)−cos(0))|  (Formula 26)

[0150] and, as in the above-described case of performing directiondetection, counts in two areas which are not the zero cross areas arerepresented by

DAT[n+1]=T _(c)cos(φ+60)−T _(c)cos(φ)  (Formula 27)

DAT[n+2]=T _(c)cos(φ+120)−T _(c)cos(φ+60)  (Formula 28)

[0151] A maximum value of |DAT[n]| within this range is represented by

[0152] when φ=0, 60°,

|DAT[n]|=0.5T _(c)

[0153] Likewise, minimum values of DAT[n+1] and DAT[n+2] are representedby

[0154] when φ=0°,

|DAT[n+1]=0.5T _(c)

[0155] when φ=60°,

|DAT[n+2]|=0.5T _(c)

[0156] According, also in this case, the following relationship alwaysholds.

|DAT[n]|≧|DAT[n+1],|DAT[n+2]|

[0157] Next, an example of specific operation according to the thirdembodiment will be described.

[0158] Initially, the optical disc 102 is rotated at a predeterminedrotation speed. After the traverse drive means 110 and the trackingactuator 111 are disabled, the count of the count means 115 is obtainedfor every rotation angle of 60 degrees. At this time, the count isobtained by any of the following methods: a method of obtaining thecount with direction detection for an area which is judged as a zerocross area by the zero cross area detection means 301 while obtainingthe count without direction detection for other areas; a method ofobtaining the count with direction detection and the count withoutdirection detection separately, and selecting the count with directiondetection for the zero cross area while selecting the count withoutdirection detection for other areas; and a method of obtaining the countwith direction detection and the count without direction detection atthe same time, and selecting the count with direction detection for thezero cross area while selecting the count without direction detectionfor other areas. Further, an area that adopts the data without directiondetection can obtain the same count as that with direction detection byadding the sign of a just previous area that adopts the data withdirection detection, or by adding the sign of a further previous area ifthe just previous area adopts the data without direction detection.

[0159] As described above, according to the third embodiment of thepresent invention, since the zero cross area detection means 301 isprovided, the track cross, detection method is switched between the areawhere the track cross speed has the lowest value and the other areas,among the areas divided with the rotation angle obtained by the rotationangle detection means 114, and track counting is carried out withdirection detection for the area where the track cross speed has thelowest value while it is carried out without direction detection for theother areas, whereby the optimum track counting method can be selectedaccording to variations in the track cross speed, and accurate vibrationdetection can be carried out at all times.

[0160] (Embodiment 4)

[0161] Hereinafter, an information disc recording/playback apparatus anda vibration detection method for the information disc recording/playbackapparatus according to a fourth embodiment of the present invention willbe described taking a DVD-ROM player as an example, with reference toFIG. 1.

[0162] Since the fundamental construction of the apparatus is identicalto that of the first embodiment, repeated description is not necessary.Next, an example of specific operation of this fourth embodiment will bedescribed employing the rotation angle detection means 114.

[0163] A DVD-ROM disc loaded on the DVD-ROM player 101 is fixed to thedisc rotation means 103. Next, focus search is carried out with a laserfor CD-ROM, and the amplitude of a focus error signal is measured. As aresult, the DVD-ROM disc is judged as a ROM disc because itsreflectivity is relatively high. Next, the DVD-ROM disc is rotated at apredetermined speed by the disc rotation means 103, and the degree ofmodulation of an RF signal is measured. The measured degree ofmodulation is compared with a reference value, whereby the disc isjudged as a DVD disc. Consequently, the disc judgement result is aDVD-ROM.

[0164] In this fourth embodiment, the DVD-ROM disc is able to perform8X-speed playback at 4590 rpm (maximum speed), 5X-speed playback at 2870rpm, and 2.5X-speed playback at 1435 rpm, and a low speed at which novibration occurs is 1435 rpm. Vibration detection is carried out at 3000rpm and 400 rpm, and it is judged whether or not the detected vibrationamounts are lower than an allowable vibration amount at the 5X-speed andthe 8X-speed, respectively. Further, the allowable vibration amount is100 μm.

[0165] Initially, the DVD-ROM disc is rotated at 1435 rpm that is asufficiently low speed at which no vibration occurs between the disc andthe reading means 104. After the traverse drive means 110 and thetracking actuator 111 are disabled, the count of the count means 115 isobtained at every rotation angle of 60 degrees. Since no vibrationoccurs between the disc and the reading means 104, the count due to onlythe eccentricity component between the disc and the reading means 104 isobtained. For example, the count may be obtained by a method ofperforming counting for plural rotations with one rotation as a unit,and averaging the obtained counts, or a method of performing countingfor plural rotations as described above, and selecting, from theobtained counts, plural counts which are not supposed to be falsecounts.

[0166] For example, it is assumed that the data measured for fourrotations with direction detection in each of the six-divided areas, andthe average of the measured data in each area are as follows: TABLE 1counts at 1400 rpm No. area [0] area [1] area [2] area [3] area [4] area[5] 1 57 39 −17 −57 −35 18 2 59 39 −20 −55 −35 18 3 57 37 −18 −57 −34 224 57 39 −18 −59 −33 14 average 57.5 38.5 −18.3 −57.0 −34.3 18.0

[0167] Likewise, counting is carried out at 3000 rpm. When it is assumedthat the counts at 3000 rpm are as follows: TABLE 2 counts at 3000 rpmNo. area [0] area [1] area [2] area [3] area [4] area [5] 1 71 49 −21−69 −48 18 2 71 49 −22 −69 −49 19 3 72 49 −22 −69 −49 18 4 72 51 −20 −71−50 18 average 71.5 49.5 −21.25 −69.5 −49 18.25

[0168] a difference between the @ average values of the track countsobtained at 1435 rpm and 3000 rpm in each area is represented by TABLE 3counts at 3000 rpm-1400 rpm DAT [0] DAT [1] DAT [2] DAT [3] DAT [4] DAT[5] 14.0 11.0 −3.0 −12.5 −14.8 0.3

[0169] and, these counts are track counts due to vibration.

[0170] In order to obtain the vibration amount from the data shown in(Table 3), these data are substituted into (Formula 12) and (Formula13), whereby 12 pieces of data are obtained as follows: TABLE 4calculated vibration amounts (3000 rpm-1400 rpm) vibration vibrationvibration vibration vibration vibration amount amount amount amountamount amount 1 [0] 1 [1] 1 [2] 1 [3] 1 [4] 1 [5] 44 44 39 48 52 48 4441 57 43 50 39

[0171] By averaging these 12 pieces of data, the vibration amount isobtained as follows.

[0172] vibration amount=46 tracks

[0173] Further, since this disc is a DVD-ROM disc, the vibration amountis multiplied by the track pitch of 0.74 μm, whereby the vibrationamplitude is obtained as follows.

[0174] vibration amplitude=34.04 [μm]

[0175] Since the allowable maximum vibration amount of the system is 100μm and the obtained vibration amplitude is lower than the allowablevalue, the disc can be rotated at the 5X-speed, i.e., 2870 rpm.

[0176] Next, counting is carried out at 4000 rpm. When it is assumedthat the counts at 4000 rpm are as follows: TABLE 5 counts at 4000 rpmNo. area [0] area [1] area [2] area [3] area [4] area [5] 1 −61 86 13353 −78 −132 2 −62 86 132 53 −78 −133 3 −61 85 132 56 −78 −133 4 −62 82133 56 −75 −133 average −61.5 84.75 132.5 54.5 −77.25 −132.75

[0177] a difference between the average values of the track countsobtained at 1435 rpm and 3000 rpm in each area is represented by TABLE 6counts at 4000 rpm-1400 rpm DAT [0] DAT [1] DAT [2] DAT [3] DAT [4] DAT[5] −119.0 46.3 150.8 111.5 −43.0 −150.8

[0178] and, these counts are track counts due to vibration.

[0179] In order to obtain the vibration amount from the data shown in(Table 3), these data are substituted into (Formula 12) and (Formula13), whereby 12 pieces of data are obtained as follows: TABLE 7calculated vibration amounts (4000 rpm-1400 rpm) vibration vibrationvibration vibration vibration vibration amount amount amount amountamount amount 1 [0] 1 [1] 1 [2] 1 [3] 1 [4] 1 [5] 171 154 156 159 155159 159 162 155 156 168 154

[0180] By averaging these 12 pieces of data, the vibration amount isobtained as follows.

[0181] vibration amount=159 tracks

[0182] Further, since this disc is a DVD-ROM disc, the vibration amountis multiplied by the track pitch of 0.74 μm, whereby the vibrationamplitude is obtained as follows.

[0183] vibration amplitude=117.66 [μm]

[0184] Since the allowable maximum vibration amount of the system is 100μm and the obtained vibration amplitude is higher than the allowablevalue, the disc cannot be rotated at the 8X-speed, i.e., 4590 rpm, andtherefore, the maximum rotation speed is set at the 5X-speed.

[0185] Hereinafter, a description will be given of the reason why thevibration amount, the vibration speed, and the vibration accelerationcan be expressed by (Formula 12)˜(Formula 17), using the signed countsobtained with direction detection.

[0186] When the track count area is divided into six sections at every60 degrees and counting is carried out for each section, the count ineach section is represented by (Formula 29), assuming that therespective sections are 0˜5, the vibration amount is Tc, and the phaseangle of the track displacement amount at a starting point in section 0is φ.

DAT[n]=T _(c)cos(30n+φ)−T _(c)cos(30n+φ−60)  (Formula 29)

[0187] When the data in the respective sections 0˜5 are DAT[0]=a,DAT[1]=b, DAT[2]=c, DAT[3]=−a, DAT[4]=−b, DAT[5]=−c, from (Formula 29),DAT[0] is represented by $\begin{matrix}{{{{DAT}\lbrack 0\rbrack} = {T_{c}( {{\cos (\varphi)} - {\cos ( {\varphi - 60} )}} )}}\begin{matrix}{\quad {= {T_{c}( {{\cos (\varphi)} - {{\cos (\varphi)}{\cos (60)}} + {{\sin (\varphi)}{\sin (60)}}} )}}} \\{= {T_{c}( {{\frac{1}{2}{\cos (\varphi)}} + {\frac{\sqrt{3}}{2}{\sin (\varphi)}}} )}} \\{= {T_{c}{\sin ( {\varphi + \alpha_{1}} )}}}\end{matrix}} & ( {{Formula}\quad 30} ) \\{{{{Since}\quad {\sin ( \alpha_{1} )}} = \frac{\sqrt{3}}{2}},{{\cos ( \alpha_{1} )} = \frac{1}{2}},\begin{matrix}{\quad {\alpha_{1} = 60}} \\{\quad {{\therefore{{DAT}\lbrack 0\rbrack}} = {T_{c}{\sin ( {\varphi + 60} )}}}} \\{\quad {= a}}\end{matrix}} & \quad\end{matrix}$

[0188] Likewise, DAT[1] is represented by $\begin{matrix}\begin{matrix}{{{{DAT}\lbrack 0\rbrack} = {T_{c}( {{\cos ( {\varphi + 60} )} - {\cos (\varphi)}} )}}\begin{matrix}{\quad {= {T_{c}( {{{\cos (\varphi)}{\cos (60)}} - {{\sin (\varphi)}{\sin (60)}} - {\cos (\varphi)}} )}}} \\{= {T_{c}( {{\frac{1}{2}{\cos (\varphi)}} - {\frac{\sqrt{3}}{2}{\sin (\varphi)}}} )}} \\{= {T_{c}{\sin ( {\varphi + \alpha_{2}} )}}}\end{matrix}} \\{{{{Since}\quad {\sin ( \alpha_{2} )}} = \frac{\sqrt{3}}{2}},{{\cos ( \alpha_{2} )} = \frac{1}{2}},\begin{matrix}{\quad {\alpha_{2} = {- 60}}} \\{\quad {{\therefore{{DAT}\lbrack 1\rbrack}} = {T_{c}{\sin ( {\varphi - 60} )}}}} \\{\quad {= b}}\end{matrix}}\end{matrix} & ( {{Formula}\quad 31} )\end{matrix}$

[0189] From (Formula 30), $\begin{matrix}{{\sin ( {\varphi + 60} )} = \frac{a}{T_{c}}} & ( {{Formula}\quad 32} )\end{matrix}$

[0190] Then, (Formula 31) is represented by $\begin{matrix}{{{{DAT}\lbrack 1\rbrack} = {T_{c}{\sin ( {\varphi + 60 - 120} )}}}\begin{matrix}{= {T_{c}( {{{\sin ( {\varphi + 60} )}{\cos ( {- 120} )}} + {{\sin ( {- 120} )}{\cos ( {\varphi + 60} )}}} )}} \\{= {T_{c}( {{{- \frac{1}{2}}{\sin ( {\varphi + 60} )}} - {\frac{\sqrt{3}}{2}{\cos ( {\varphi + 60} )}}} )}} \\{= {T_{c}( {{{- \frac{1}{2}}{\sin ( {\varphi + 60} )}} \mp {\frac{\sqrt{3}}{2}\sqrt{1 - {\sin^{2}( {\varphi + 60} )}}}} )}} \\{= {{T_{c}( {{{- \frac{1}{2}}\frac{a}{T_{c}}} \mp {\frac{\sqrt{3}}{2}\sqrt{1 - ( \frac{a}{T_{c}} )^{2}}}} )} = b}}\end{matrix}} & ( {{Formula}\quad 33} )\end{matrix}$

[0191] Accordingly, $\begin{matrix}\begin{matrix}{{{{- \frac{1}{2}}a} \mp {\frac{\sqrt{3}}{2}\sqrt{T_{c}^{2} - a^{2}}}} = b} \\{{{\mp \frac{\sqrt{3}}{2}}\sqrt{T_{c}^{2} - a^{2}}} = {b + {\frac{1}{2}a}}} \\{{\frac{3}{4}( {T_{c}^{2} - a^{2}} )} = {b^{2} + {ab} + {\frac{1}{4}a}}} \\{T_{c} = {{\pm \frac{2}{\sqrt{3}}}\sqrt{a^{2} + {ab} + b^{2}}}}\end{matrix} & ( {{Formula}\quad 34} )\end{matrix}$

[0192] Likewise, since DAT[0]=a, DAT[2]=c, $\begin{matrix}{T_{c} = {{\pm \frac{2}{\sqrt{3}}}\sqrt{a^{2} - {ac} + c^{2}}}} & ( {{Formula}\quad 35} )\end{matrix}$

[0193] and, therefore, (Formula 12) and (Formula 13) are derived from(Formula 34) and (Formula 35).

[0194] Furthermore, the track cross due to the eccentricity or vibrationis represented by a sinusoidal wave as follows, using the Tc, phaseangle φ, and angular velocity ω.

f(t)=T _(c)cos(ωt+φ)  (Formula 36)

[0195] Then, the absolute value of the track cross speed is obtained bydifferentiating (Formula 36) as follows. $\begin{matrix}{| \frac{{f(t)}}{t} | =  {\omega \quad T_{c}} \middle| {\sin ( {{\omega \quad t} + \varphi} )} |} & ( {{Formula}\quad 37} )\end{matrix}$

[0196] Since ω=2πf, and f=Vrpm/60 (Vrpm: present rotation speed [rpm]),$\begin{matrix}{\begin{matrix}{{\text{|}\frac{{f(t)}}{t}\text{|}} =  {2\pi \quad {fT}_{c}} \middle| {\sin ( {{\omega \quad t} + \varphi} )} |} \\{= {\frac{2\pi \quad V_{rpm}}{60}T_{c}\text{|}{\sin ( {{\omega \quad t} + \varphi} )}\text{|}}}\end{matrix}} & ( {{Formula}\quad 38} )\end{matrix}$

[0197] Since (Formula 38) becomes maximum when

|sin(ωt+φ)|=1  (Formula 39)

[0198] (Formula 14) and (Formula 15) are derived from (Formula 34) and(Formula 35), respectively.

[0199] Furthermore, the absolute value of the track cross accelerationis obtained by differentiating (Formula 38) as follows. $\begin{matrix}{| \frac{^{2}{f(t)}}{t^{2}} | =  ( \frac{2\pi \quad V_{rpm}}{60} )^{2} \middle| {\cos ( {{\omega \quad t} + \varphi} )} |} & ( {{Formula}\quad 40} )\end{matrix}$

[0200] Since (Formula 27) becomes maximum when

cos(ωt+φ)=1  (Formula 41)

[0201] (Formula 16) and (Formula 17) are derived from (Formula 34) and(Formula 35), respectively.

[0202] As described above, according to the fourth embodiment of thepresent invention, when the vibration amplitude, or vibration speed, orvibration acceleration is evaluated considering the track pitch of theoptical disc 102, it is calculated at every predetermined rotation angleand an average of the results of calculation is obtained, and a maximumrotation speed that is lower than the allowable vibration amplitude, orvibration speed, or vibration acceleration of the information discrecording/playback apparatus is determined on the basis of the average.Therefore, vibration detection can be carried out more accurately ascompared with the first embodiment, using a single threshold value,independently of the type of the information disc.

[0203] While in this fourth embodiment, setting of the maximum rotationspeed of the DVD-ROM disc is described, the maximum rotation speeds ofother types of discs having different track pitches, such as a CD-ROMdisc having a track pitch of 1.6 μm or a DVD-R3.9G disc having a trackpitch of 0.8 μm, can also be obtained by judging as to whether themeasured maximum vibration amount is lower than the allowable one, usingthe standard track pitch of each disc and the vibration amount.

[0204] Further, while in this fourth embodiment the vibration amount isobtained on the basis of the average of 12 pieces of data, the vibrationamount may be obtained using the average of m pieces of central valuesselected from the 12 pieces of data which are arranged in the order ofsize, or using a value in proportion to the average.

[0205] Furthermore, while in this fourth embodiment the maximum playbackspeed is set on the basis of the vibration amplitude, the maximumplayback speed may be set using a value in proportion to the vibrationamplitude or a value in proportion to the second power of the vibrationamplitude. Alternatively, the maximum playback speed may be set on thebasis of the vibration speed or a value in proportion to the vibrationspeed or the second power of the vibration speed, using (Formula 14) and(Formula 15) as well as the disc rotation speed. Further, the maximumplayback speed may be set on the basis of the vibration accelerationspeed or a value in proportion to the vibration acceleration speed orthe second power of the vibration acceleration speed, using (Formula 16)and (Formula 17) as well as the disc rotation speed.

[0206] Moreover, while in this fourth embodiment the maximum playbackspeed is set on the basis of the data obtained for four rotations eachrotation being divided into six areas, the maximum playback speed may beobtained by measuring data corresponding to continuous two or moreareas.

[0207] (Embodiment 5)

[0208] Hereinafter, an information disc recording/playback apparatus anda vibration detection method for the information disc recording/playbackapparatus according to a fifth embodiment of the present invention willbe described taking a DVD-ROM player as an example, with reference toFIG. 4.

[0209] In FIG. 4, the same reference numerals as those shown in FIG. 1denote the same or corresponding parts, and reference numeral 116 adenotes a control means having a linear speed detection means 401 and aplayback speed detection means 402. The linear speed detection means 401detects the linear speed of the disc. For example, the linear speed isdetected as follows. An address value at a certain radial position ispreviously read, one-track jumping is carried out, an address value atthe destination of the track jumping is read, and a difference betweenthe address values is obtained as the linear speed. Alternatively, thelength of one rotation of the disc is obtained from a radial position,and the linear speed of the disc is obtained on the basis of the radioof the length to the difference between the previously obtained addressvalues for one rotation. The playback speed detection means 402 detectsthe current playback speed. For example, the current playback speed isobtained from the cycle of a PLL which generates a data playback clock,or it is obtained on the basis of the cycle of a frame clock which isoutputted for every frame of data.

[0210] Next, a description will be given of the operation for obtainingthe track pitch.

[0211] Generally, assuming that the track pitch of the disc is Tp, thelinear speed is V1, the current address position is Ad, the currentradial position is r, the radial position at the innermost radius is R0,and the address value included in the unit time is Adunit, the followingrelationship holds. $\begin{matrix}{\frac{\pi ( {r^{2} - R_{0}^{2}} )}{T_{p}} = \frac{V_{1}{Ad}}{{Ad}_{unit}}} & ( {{Formula}\quad 42} )\end{matrix}$

[0212] Further, assuming that the current rotation speed is Vrpm, theplayback speed V2 at the radial position r is represented by$\begin{matrix}{V_{2} = {\frac{2\pi \quad r}{V_{1}}\frac{V_{rpm}}{60}}} & ( {{Formula}\quad 43} )\end{matrix}$

[0213] Therefore, assuming that the linear speed is V1, the currentaddress value is Ad, and the current rotation speed is Vrpm, the trackpitch Tp is represented by $\begin{matrix}{T_{p} = {{\pi \lbrack {( \frac{60V_{1}V_{2}}{2\pi \quad V_{rpm}} )^{2} - R_{0}^{2}} \rbrack}\frac{{Ad}_{unit}}{V_{1}{Ad}}}} & ( {{Formula}\quad 44} )\end{matrix}$

[0214] Accordingly, the track pitch Tp can be obtained by furthermeasuring the current playback speed V2 at a certain address Ad.

[0215] Although the address Ad at which the current playback speed V2 isobtained may be an arbitrary address, when measurement is carried out atan outer radial position, the accuracy is improved.

[0216] For example, assuming that a CD-ROM disc has

[0217] linear speed V1=1.25 m/s

[0218] playback speed measurement address AD=60:00:00 =270000[frame]

[0219] rotation speed=5300 rpm

[0220] playback speed=23.8X

[0221] according to the standard of CD-ROM,

[0222] Adunit =75[frame]

[0223] R0=0.0249 [m]

[0224] are obtained, and these values are substituted into (Formula 44)to obtain the track pitch as follows.

[0225] Tp=1.573 [μm]

[0226] As described above, according to the fifth embodiment, when amove distance detection means for detecting the move distance of thereading means 104 is provided, accurate vibration detection can alwaysbe carried out by measuring the accurate track pitch, even when thetrack pitch is different from the standard value that is set for eachdisc type. Furthermore, when the track pitch is obtained from the linearspeed, address value, and playback speed, accurate vibration detectioncan always be carried out by measuring the accurate track pitch, evenwhen the track pitch is different from the standard value that is setfor each disc type, with reduced cost, without the necessity of adding amove distance detection means.

[0227] While in this fifth embodiment the track pitch of a CD-ROM discis obtained, the track pitches of discs based on other standards, suchas a DVD or a DVD-R3.9G, can be obtained in like manner as describedabove.

[0228] Further, while in this fifth embodiment the track pitch isobtained from the linear speed, address value, and playback speed, thetrack pitch may be obtained as follows. As shown in FIG. 10, the controlmeans 116 b is provided with a move distance detection means 403 fordetecting the move distance of the reading means 104, and the readingmeans 104 is moved while counting the number of tracks, and the trackpitch is obtained as follows.

[0229] Tp=move distance/number of crossed tracks

[0230] (Embodiment 6)

[0231] Hereinafter, an information disc recording/playback apparatus anda vibration detection method for the information disc recording/playbackapparatus according to a sixth embodiment of the present invention willbe described taking a DVD-ROM player as an example, with reference toFIG. 5.

[0232] In FIG. 5, the same reference numerals as those shown in FIG. 1denote the same or corresponding parts, and reference numeral 501denotes a variable filter means having a function of shaping the trackcross pulses detected by the track cross detection means 112 so that thepulses whose widths are narrower than a predetermined value, among thedetected pulses, are not counted.

[0233] Hereinafter, a method of actually setting the variable filtermeans 501 will be described.

[0234] When setting the variable filter means 501, initially, the totalnumber of track crosses for one or more rotation is counted by themethod in which the track cross direction is not detected. At this time,it is necessary to set an initial set value of the variable filter means501, and usually, this initial value must be set at such a value thatthe minimum track count pulse width corresponding to the maximum trackcross speed is surely counted when an eccentricity between the disc andthe turn table and a maximum vibration amplitude estimated at its rpmoccur.

[0235] Assuming that the counted number of track crosses is 4Tc perrotation, the maximum track cross speed can be obtained as follows.

[0236] Initially, the track cross due to the eccentricity or vibrationis expressed by a sinusoidal wave. Using the above-mentioned Tc, phaseangle φ, and angular velocity ω, the track

[0237] cross is represented by (Formula 45)

f(t)=T _(c)cos(ωt+φ)  (Formula 45)

[0238] Then, the absolute value of the track cross speed is obtained bydifferentiating (Formula 32) as follows. $\begin{matrix}{| \frac{{f(t)}}{t} | =  {\omega \quad T_{c}} \middle| {\sin ( {{\omega \quad t} + \varphi} )} |} & ( {{Formula}\quad 46} )\end{matrix}$

[0239] Since ω=2πf, and f=Vrpm/60 (Vrpm: current rotation speed [rpm]),$\begin{matrix}\begin{matrix}{{\text{|}\frac{{t(t)}}{t}\text{|}} =  {2\pi \quad {fT}_{c}} \middle| {\sin(  {{\omega \quad t} + \varphi} | } } \\{= {\frac{2\pi \quad V_{rpm}}{60}T_{c}\text{|}{\sin ( {{\omega \quad t} + \varphi} )}\text{|}}}\end{matrix} & ( {{Formula}\quad 47} )\end{matrix}$

[0240] Accordingly, the maximum track cross speed is represented by$\begin{matrix}{{{maximum}\quad {track}\quad {cross}\quad {speed}} = {\frac{2\pi \quad V_{rpm}}{60}T_{c}}} & ( {{Formula}\quad 48} )\end{matrix}$

[0241] and, the maximum track cross speed can be obtained from the valueof Tc.

[0242] The minimum track count pulse width is calculated on the basis ofthe maximum track cross speed. Assuming that the maximum track crossspeed is Vmax[tracks/s], as two positive/negative pulses are outputtedper track, the minimum track count pulse width is represented by$\begin{matrix}{{{minimum}\quad {track}\quad {count}\quad {pulse}\quad {width}} = {\frac{1}{2V_{\max}}\lbrack s\rbrack}} & ( {{Formula}\quad 49} )\end{matrix}$

[0243] Thereby, the minimum track count pulse width of the variablefilter means 501 is set. For example, when the total number of countedtracks per rotation at 3000 rpm is 287, the maximum track cross speed isrepresented as follows:

[0244] Initially, since

T _(c)=287/4=71.75

[0245] and, from (Formula 18),

Vmax =22.54 kHz

[0246] and, therefore, the minimum track count pulse width is 22.18 μsfrom (Formula 49).

[0247] The variable filter means 501 is set on the basis of this valueso that pulses whose widths are narrower than the minimum track countpulse obtained by the above calculation are also counted, consideringvariations in the duty ratio of the normal pulse width, or the like.

[0248] In this sixth embodiment, the variable filter means 501 is set sothat a pulse having a width of up to 5.54 μs, which is one fourth of22.18 μs, is counted as a track cross signal.

[0249] During high-speed driving, the duty ratio of the track countpulse might significantly vary due to an influence of vibration in thefocusing direction, a reduction in the amplitude level of the detectionsignal for track counting, or the like. In this case, the variablefilter means 501 may be set so that a pulse having a narrower width iscounted if driving at a speed higher than a predetermined value isexpected, while in the above example a value obtained by dividing thecalculated minimum track count pulse width by a predetermined value isemployed as a set value of the filter means 501.

[0250] When the track counting is performed by the method in which asigned count is outputted because direction detection is carried out,the calculation method is somewhat different from that mentioned above.For example, in the system of outputting rotation angle informationobtained by dividing one rotation into six areas, assuming that thecount in each area for one rotation is

[0251] DAT[n]=DAT[0],DAT[1],DAT[2],DAT[3],DAT[4],DAT[5]

[0252] (when n>5, n=n mod 6 (a remainder of n being divided by 6), themaximum track cross speed becomes as represented by (Formula 19) or(Formula 20). Thereby, data of plural maximum track cross speeds areobtained, and the minimum track count pulse width may be set similarlyby using the average of these data, or the average of m pieces ofcentral values of these data, or the like.

[0253] As described above, according to the sixth embodiment of thepresent invention, setting of the track cross filter by the variablefilter means 501 is carried out on the basis of the track cross countand the current rpm, so that the pulses whose widths are narrower than apredetermined value are not counted. Therefore, even when the trackcross speed varies significantly due to the eccentricity or vibration ofthe disc, track counting most suitable for vibration detection can beaccurately carried out at all times.

[0254] Furthermore, setting of the minimum track count pulse width maybe carried out only once before obtaining the track count for detectingthe vibration amount at each rotation speed, or it may be carried outevery time the data (count) for detecting the vibration amount isobtained.

[0255] (Embodiment 7)

[0256] Hereinafter, an information disc recording/playback apparatus anda vibration detection method for the information disc recording/playbackapparatus according to a seventh embodiment of the present inventionwill be described taking a DVD-ROM player as an example, with referenceto FIGS. 5 and 6.

[0257] Usually, a general purpose microcomputer having a relativelysmall size is employed as a control means for computer peripheralequipment such as a DVD-ROM player. Such microcomputer is basicallyadaptive to integer arithmetic only, and therefore, floating-pointarithmetic or square root trigonometric function must be dealt with bysoftware.

[0258] In the calculation formula (Formula 19) or (Formula 20) which isemployed when the track counting is carried out by the method in which asigned count is outputted because direction detection is carried out asdescribed for the sixth embodiment, it is necessary to obtain squareroots, resulting in a problem that the number of program steps and thetime required for arithmetic are increased in the system as describedabove. Therefore, in this case, assuming that

[0259] DAT[n]=DAT[0],DAT[1],DAT[2],DAT[3],DAT[4],DAT[5]

[0260] (when n>5, n=n mod 6 (a remainder of n being divided by 6), andthe rotation speed of the disc rotation means is Vrpm[rpm],

4T _(c) =|DAT[0]|+|DAT[1]|+|DAT[2]|+|DAT[3]|+|DAT[4]|+|DAT[5]|  (Formula50)

[0261] $\begin{matrix}{{{maximum}\quad {track}\quad {cross}\quad {speed}} = {{\frac{2\pi \quad V_{rpm}}{60}T_{c}\frac{1}{\cos \frac{\pi}{6}}} = {\frac{2\pi \quad V_{rpm}}{60}T_{c}\frac{2}{\sqrt{3}}}}} & ( {{Formula}\quad 51} )\end{matrix}$

[0262] and, therefore, the maximum track cross speed can be calculatedwith reduced number of program steps and reduced arithmetic time, andthe variable filter means can be set on the basis of the maximum trackcross speed.

[0263] This is explained as follows with reference to FIG. 6.

[0264]FIG. 6 is a graph illustrating the amount of displacement of thecount at every rotation angle, which displacement is caused by vibrationor eccentricity.

[0265] Initially, the track cross due to eccentricity or vibration isexpressed as a sinusoidal wave, in like manner as described for thesixth embodiment. Using the Tc, phase angle φ, and angular speed ω, thetrack cross is represented by $\begin{matrix}{{\sin ( {\varphi + 60} )} = \frac{a}{T_{c}}} & ( {{Formula}\quad 52} )\end{matrix}$

[0266] Then, this is divided at every 60 degrees by dividing onerotation into six sections, as shown in FIG. 6. In FIG. 6, 601 shows awaveform when φ=0, and 602 shows a waveform when φ=30°.

[0267] For example, when φ=0, assuming that the data corresponding to0˜60°, 60˜120°, 120˜180°, . . . are DAT[0], DAT[1], DAT[2], . . . ,respectively, the respective data are represented as follows.$\begin{matrix}\begin{matrix}{\quad {{{DAT}\lbrack 0\rbrack} = {{T( {{\cos (60)} - {\cos (0)}} )} = {{- \frac{1}{2}}T_{c}}}}} \\{\quad {{{DAT}\lbrack 1\rbrack} = {{T_{c}( {{\cos (120)} - {\cos (60)}} )} = {- T_{c}}}}} \\{\quad {{{DAT}\lbrack 2\rbrack} = {{T_{c}( {{\cos (180)} - {\cos (120)}} )} = {{- \frac{1}{2}}T_{c}}}}} \\{\quad {{{DAT}\lbrack 3\rbrack} = {{T_{c}( {{\cos (240)} - {\cos (180)}} )} = {\frac{1}{2}T_{c}}}}} \\{\quad {{{DAT}\lbrack 4\rbrack} = {{T_{c}( {{\cos (300)} - {\cos (240)}} )} = T_{c}}}} \\{\quad {{{DAT}\lbrack 5\rbrack} = {{T_{c}( {{\cos (360)} - {\cos (300)}} )} = {\frac{1}{2}T_{c}}}}}\end{matrix} & ( {{Formula}\quad 53} )\end{matrix}$

[0268] In this case, the Tc calculated from (Formula 21) becomes thesame as the original value of the Tc.

[0269] However, in the case where the boundary of the areas divided atevery 60 degrees as described above does not agree with the positionwhere the track move direction is inverted (in the case of the waveform601 when φ=0, the position 603 or 604), the Tc calculated by (Formula21) becomes smaller than the original Tc, and the calculated maximumtrack cross speed also becomes lower than the original value. When theTc takes the smallest value, the waveform and divided-area as shown by602 are obtained when φ=−30°. At this time, the respective data arerepresented as follows. $\begin{matrix}\begin{matrix}{\quad {{{DAT}\lbrack 0\rbrack} = {{T( {{\cos (30)} - {\cos ( {- 30} )}} )} = 0}}} \\{\quad {{{DAT}\lbrack 1\rbrack} = {{T_{c}( {{\cos (90)} - {\cos (30)}} )} = {{- \frac{\sqrt{3}}{2}}T_{c}}}}} \\{\quad {{{DAT}\lbrack 2\rbrack} = {{T_{c}( {{\cos (150)} - {\cos (90)}} )} = {{- \frac{\sqrt{3}}{2}}T_{c}}}}} \\{\quad {{{DAT}\lbrack 3\rbrack} = {{T_{c}( {{\cos (210)} - {\cos (150)}} )} = 0}}} \\{\quad {{{DAT}\lbrack 4\rbrack} = {{T_{c}( {{\cos (270)} - {\cos (210)}} )} = {\frac{\sqrt{3}}{2}T_{c}}}}} \\{\quad {{{DAT}\lbrack 5\rbrack} = {{T_{c}( {{\cos (330)} - {\cos (270)}} )} = {\frac{\sqrt{3}}{2}T_{c}}}}}\end{matrix} & ( {{Formula}\quad 54} )\end{matrix}$

[0270] Therefore, the Tc calculated from (Formula 21) becomes 0.866times the original Tc. Accordingly, when the track counting is carriedout by the method in which a signed count is outputted because directiondetection is carried out, a value smaller than the original Tc, i.e.,0.866 times the original Tc at the worst, is calculated. Consideringthis effect, when calculating the maximum track cross speed on the basisof the Tc calculated from (Formula 21), (Formula 22) represents themaximum track cross speed including the expected error.

[0271] As described above, according to the seventh embodiment, themaximum track cross speed including an expected error is calculated onthe basis of the signed track cross count and the current rpm, and thetrack cross filter is set on the basis of the maximum track cross speed.Therefore, track counting most suitable for vibration detection can beaccurately carried out at all times, without necessity of performingadditional counting without signs or calculating square roots whichrequire many program steps.

[0272] (Embodiment 8)

[0273] Hereinafter, an information disc recording/playback apparatus anda vibration detection method for the information disc recording/playbackapparatus according to an eighth embodiment of the present inventionwill be described taking a DVD-ROM player as an example, with referenceto FIG. 5. The fundamental construction is identical to that shown inFIG. 5 and, therefore, the distinctive operation of this eighthembodiment will be mainly described hereinafter.

[0274] When setting the variable filter means 501, initially, the totalnumber of track crosses for one or more rotation is counted by themethod in which the track cross direction is not detected. At this time,it is necessary to set an initial set value of the variable filter means501, and usually, this initial value must be set at such a value thatthe minimum track count pulse width corresponding to the maximum trackcross speed is surely counted when an eccentricity between the disc andthe turn table and a maximum vibration amplitude estimated at its rpmoccur.

[0275] Assuming that the counted number of track crosses is 4Tc perrotation, the maximum track cross speed is represented by (Formula 55),using the Tc, phase angle φ, and angular velocity ω. $\begin{matrix}{{{maximum}\quad {track}\quad {cross}\quad {speed}} = {\frac{2\pi \quad V_{rpm}}{60}T_{c}}} & ( {{Formula}\quad 55} )\end{matrix}$

[0276] On the basis of this maximum track cross speed, the minimum trackcount pulse width is calculated. Assuming that the maximum track crossspeed is Vmax [tracks/s], since two positive/negative pulses areoutputted per track, the minimum track count pulse width is representedby $\begin{matrix}{{{minimum}\quad {track}\quad {count}\quad {pulse}\quad {width}} = {\frac{1}{2V_{\max}}\lbrack s\rbrack}} & ( {{Formula}\quad 56} )\end{matrix}$

[0277] and the minimum track count pulse width of the variable filtermeans 501 is set according to the above formula.

[0278] Further, setting the minimum track count pulse width is carriedout every time the data (count) for performing detection of thevibration amount is obtained. When the value of the minimum track countpulse width varies by a predetermined value or more at the same rotationspeed, there is a high possibility of false track counting of theprevious counts because an optimum track count filter has not been set,and therefore, the value of the minimum track count pulse width isdiscarded, and only the counts after the change should be adopted as thecounts for vibration detection.

[0279] As described above, according to the eighth embodiment, thecounts obtained before the set value of the variable filter means 501has changed by a predetermined value or more are not used because thepossibility of false counting is high. Therefore, track counting mostsuitable for vibration detection can be accurately carried out at alltimes.

[0280] (Embodiment 9)

[0281] Hereinafter, an information disc recording/playback apparatus anda vibration detection method for the information disc recording/playbackapparatus according to a ninth embodiment of the present invention willbe described taking a DVD-ROM player as an example, with reference toFIG. 7.

[0282] In FIG. 7, the same reference numerals as those shown in FIG. 1denote the same or corresponding parts, and reference numeral 701denotes a pulse width storage means for holding the width of a pulsethat is just previous to the current pulse. Reference numeral 702denotes a filter means which receives the track cross pulse outputtedfrom the track cross pulse detection means 112, and outputs it to thecount means 115. At this time, the pulse width is measured, and when themeasured pulse width is a predetermined value smaller than the pulsewidth stored in the pulse width storage means 702, this pulse isregarded as one due to false count and is not outputted.

[0283] As for the amount of change in the pulse width that is notcounted, the measured pulse width should not be counted when it becomessmaller than the just-previous pulse width by a predetermined ratio, forexample, 0.5.

[0284] As described above, according to the ninth embodiment of thepresent invention, the pulse width storage means 701 and the filtermeans 702 are provided, and when the filter means 702 judges that themeasured pulse width is a predetermined value smaller than thejust-previous pulse width which is stored in the pulse width storagemeans 701, this pulse is regarded as one due to false detection causedby noise and is not counted by the count means 115. Therefore, trackcounting most suitable for vibration detection can be accurately carriedout at all times, without requiring time for excessive measurement.

APPLICABILITY IN INDUSTORY

[0285] An information disc recording/playback apparatus and a vibrationdetection method for the information disc recording/playback apparatusaccording to the present invention are valuable as an information discrecording/playback apparatus having a vibration measurement means formeasuring vibrations caused by eccentricity of a disc, and a vibrationdetection method for the information disc recording/playback apparatus,and particularly, the apparatus and method are valuable as those havinga construction for detecting vibrations using track counting.

1. An information disc recording/playback apparatus capable of recordingor playing at least two kinds of information discs having differenttrack pitches, on which information recording tracks are formed spirallyor concentrically, said apparatus comprising: a disc rotation means forrotating the information disc at a predetermined speed; a reading meansfor reading an information signal from the disc; a drive means fordriving the reading means in the direction of the radius of the disc; atrack pitch detection means for detecting the track pitch of theinformation disc from the information disc; a track cross detectionmeans for generating track cross signals on the basis of playbacksignals that are generated when the reading means crosses theinformation tracks; a count means for counting track cross pulses thatare detected by the track cross detection means, and outputting thecount; and a control means for determining a maximum rotation speed thatis lower than an allowable vibration amplitude of the information discrecording/playback apparatus on the basis of the count and the trackpitch, or determining a maximum rotation speed that is lower than anallowable vibration speed or vibration acceleration speed of theinformation disc recording/playback apparatus on the basis of the count,the track pitch, and the current disc rotation speed, and controllingthe disc rotation means so that the disc rotation means rotates theinformation disc at a speed lower than the allowable maximum rotationspeed to record or reproduce data in/from the disc.
 2. An informationdisc recording/playback apparatus as defined in claim 1 furthercomprising: a track cross direction detection means for detecting atrack cross direction indicating the direction in which the readingmeans crosses the information tracks; a rotation angle detection meansfor outputting rotation angle information of the disc rotation means;and said count means for counting the track cross pulses with signs,which are detected by the track cross detection means, on the basis ofthe result of the detection by the track cross direction detectionmeans, and the rotation angle information outputted from the rotationangle detection means.
 3. An information disc recording/playbackapparatus as defined in claim 1 further comprising: a track crossdirection detection means for detecting a track cross directionindicating the direction in which the reading means crosses theinformation tracks; a track cross speed detection means for detectingthe frequency of the track cross pulses; a rotation angle detectionmeans for outputting rotation angle information of the disc rotationmeans; and said count means for counting the track cross pulses withsigns, which are detected by the track cross detection means, on thebasis of the result of the detection by the track cross directiondetection means and the rotation angle information outputted from therotation angle detection means, while detecting the track crossdirection by the track cross direction detection means when the resultof the detection by the track cross speed detection means indicates thatthe track cross speed is lower than a predetermined value, and countingthe track cross pulses with signs, without detecting the track crossdirection by the track cross direction detection means, on the basis ofthe track cross direction that has just previously been detected by thetrack cross direction detection means, when the result of the detectionby the track cross speed detection means indicates that the track crossspeed becomes higher than the predetermined value.
 4. An informationdisc recording/playback apparatus capable of recording or playing atleast two kinds of information discs having different track pitches, onwhich information recording tracks are formed spirally orconcentrically, said apparatus comprising: a disc rotation means forrotating the information disc at a predetermined speed; a reading meansfor reading an information signal from the disc; a drive means fordriving the reading means in the direction of the radius of the disc; atrack pitch detection means for detecting the track pitch of theinformation disc from the information disc; a track cross detectionmeans for generating track cross signals on the basis of playbacksignals that are generated when the reading means crosses theinformation tracks; a track cross direction detection means fordetecting a track cross direction indicating the direction in which thereading means crosses the information tracks; a rotation angle detectionmeans for outputting rotation angle information of the disc rotationmeans, which is divided into n areas for one rotation; a zero cross areadetection means for detecting two areas where the track cross speed hasa lowest value, from among the n areas; a count means for counting trackcross pulses with signs, which are detected by the track cross detectionmeans, on the basis of the result of the detection by the track crossdirection detection means and the rotation angle information outputtedfrom the rotation angle detection means, while detecting the track crossdirection by the track cross direction detection means, in an area wherethe track cross speed has the lowest value according to the result ofthe detection by the zero cross area detection means, counting the trackcross pulses with signs, without detecting the track cross direction bythe track cross direction detection means, on the basis of the trackcross direction that has just previously been detected by the trackcross direction detection means, in an area where the track cross speeddoes not have the lowest value according to the result of the detectionby the zero cross area detection means, and outputting the count; and acontrol means for determining a maximum rotation speed that is lowerthan an allowable vibration amplitude of the information discrecording/playback apparatus on the basis of the count and the trackpitch, or determining a maximum rotation speed that is lower than anallowable vibration speed or vibration acceleration speed of theinformation disc recording/playback apparatus on the basis of the count,the track pitch, and the current disc rotation speed, and controllingthe disc rotation means so that the disc rotation means rotates theinformation disc at a speed lower than the allowable maximum rotationspeed to record or reproduce data in/from the disc.
 5. An informationdisc recording/playback apparatus capable of recording or playing atleast two kinds of information discs having different track pitches, onwhich information recording tracks are formed spirally orconcentrically, said apparatus comprising: a disc rotation means forrotating the information disc at a predetermined speed; a reading meansfor reading an information signal from the disc; a drive means fordriving the reading means in the direction of the radius of the disc; atrack pitch detection means for detecting the track pitch of theinformation disc from the information disc; a track cross detectionmeans for generating track cross signals on the basis of playbacksignals that are generated when the reading means crosses theinformation tracks; a track cross direction detection means fordetecting a track cross direction indicating the direction in which thereading means crosses the information tracks; a rotation angle detectionmeans for outputting rotation angle information of the disc rotationmeans, which is divided into n areas for one rotation; a zero cross areadetection means for detecting two areas where the track cross speed hasa lowest value, from among the n areas; a count means including a firstcount means for counting track cross pulses with signs, which aredetected by the track cross detection means, on the basis of the resultof the detection by the track cross direction detection means and therotation angle information outputted from the rotation angle detectionmeans, and a second count means for counting the track cross pulsesdetected by the track cross detection means, without detecting the trackcross direction, on the basis of the rotation angle informationoutputted from the rotation angle detection means, said count means forobtaining a first count of the first count means when the drive means isdisabled and the information disc loaded on the disc rotation means isrotated, obtaining a second count in which a sign is added to the countof the second count means, on the basis of the track cross directionwhich has just previously been detected by the track cross directiondetection means, when the drive means is disabled and the informationdisc loaded on the disc rotation means is rotated, selecting the firstcount in an area where the track cross speed has the lowest valueaccording to the result of the detection by the zero cross areadetection means, selecting the second count in an area where the trackcross speed does not have the lowest value according to the result ofthe detection by the zero cross area detection means, and counting thetrack cross pulses for every rotation angle and outputting it; and acontrol means for determining a maximum rotation speed that is lowerthan an allowable vibration amplitude of the information discrecording/playback apparatus on the basis of the counts and the trackpitch, or determining a maximum rotation speed that is lower than anallowable vibration speed or vibration acceleration speed of theinformation disc recording/playback apparatus on the basis of thecounts, the track pitch, and the current disc rotation speed, andcontrolling the disc rotation means so that the disc rotation meansrotates the information disc at a speed lower than the allowable maximumrotation speed to record or reproduce data in/from the disc.
 6. Aninformation disc recording/playback apparatus as defined in claim 4 or5, wherein said rotation angle detection means divides the rotationangle information of the disc rotation means into six areas for eachrotation, and outputs the divided information; and said zero cross areadetection means detects, as zero cross areas, an area where the count ofthe count means has the smallest value, and an area on a diagonal linewith respect to the area.
 7. An information disc recording/playbackapparatus capable of recording or playing at least two kinds ofinformation discs having different track pitches, on which informationrecording tracks are formed spirally or concentrically, said apparatuscomprising: a disc rotation means for rotating the information disc at apredetermined speed; a reading means for reading an information signalfrom the disc; a drive means for driving the reading means in thedirection of the radius of the disc; a track pitch detection means fordetecting the track pitch of the information disc from the informationdisc; a track cross detection means for generating track cross signalson the basis of playback signals that are generated when the readingmeans crosses the information tracks; a count means for counting trackcross pulses that are detected by the track cross detection means, andoutputting the count; and a control means for using, as the count, adifference between the track cross count that is obtained when theinformation disc is rotated at a first rotation speed and at least onerotation speed that is higher than the first rotation speed, and a countthat is obtained with the at least one rotation speed higher than thefirst rotation speed, determining a maximum rotation speed that is lowerthan an allowable vibration amplitude of the information discrecording/playback apparatus on the basis of the count and the trackpitch, or determining a maximum rotation speed that is lower than anallowable vibration speed or vibration acceleration speed of theinformation disc recording/playback apparatus on the basis of the count,the track pitch, and the current disc rotation speed, and controllingthe disc rotation means so that the disc rotation means rotates theinformation disc at a speed lower than the allowable maximum rotationspeed to record or reproduce data in/from the disc.
 8. An informationdisc recording/playback apparatus as defined in claim 7, wherein thefirst rotation speed is a sufficiently low speed at which no vibrationoccurs between the information disc and the reading means, and the trackcross pulses due to the eccentricities of the information disc and thedisc rotation means are counted.
 9. An information discrecording/playback apparatus as defined in claim 7, wherein said countmeans counts the track cross pulses at the first rotation speed for apredetermined number of times, and counts the track cross pulses withthe at least one rotation speed that is higher than the first rotationspeed, for the predetermined number of times; and said control meansemploys, as the count, an average of counts for more than one time,which are selected from among the counts obtained by the above-describedrepetition, or a value in proportion to the average.
 10. An informationdisc recording/playback apparatus as defined in claim 7, wherein saidrotation angle detection means outputs the rotation angle information ofthe disc rotation means, which is divided into six areas for onerotation; and when a difference between the track cross count measuredat the first rotation speed with each of the six-divided rotationangles, and the track cross count measured with the at least onerotation speed higher than the first rotation speed is as follows:DAT[n]=DAT[0],DAT[1],DAT[2],DAT[3],DAT[4],DAT[5] (when n>5, n=n mod 6 (aremainder of n being divided by 6), the control means determines amaximum rotation speed that is lower than the allowable amplitude of theinformation disc recording/playback apparatus, on the basis of a valuein proportion to a vibration amount 1 or a vibration amount 2, or avalue in proportion to the second power of the vibration amount 1 or thesecond power of the vibration amount 2, and the track pitch, saidvibration amounts 1 and 2 being represented as follows: $\begin{matrix}{{{vibration}\quad {amount}\quad {1\lbrack n\rbrack}} = {\frac{2}{\sqrt{3}}\sqrt{| {{{DAT}\lbrack n\rbrack}^{2} + {{{DAT}\lbrack n\rbrack}{{DAT}\lbrack {n + 1} \rbrack}} + {{DAT}\lbrack {n + 1} \rbrack}^{2}} |}}} & ( {{Formula}\quad 1} ) \\{{{vibration}\quad {amount}\quad {2\lbrack n\rbrack}} = {\frac{2}{\sqrt{3}}\sqrt{| {{{DAT}\lbrack n\rbrack}^{2} - {{{DAT}\lbrack n\rbrack}{{DAT}\lbrack {n + 2} \rbrack}} + {{DAT}\lbrack {n + 2} \rbrack}^{2}} |}}} & ( {{Formula}\quad 2} )\end{matrix}$


11. An information disc recording/playback apparatus as defined in claim10, wherein said control means determines a maximum rotation speed thatis lower than the allowable amplitude of the information discrecording/playback apparatus, on the basis of a value in proportion toan average of twelve vibration amounts 1 or vibration amounts 2 whichare calculated for n=0˜5 according to,(Formula 1) or (Formula 2), andthe track pitch, or a value in proportion to an average of m pieces ofcentral values selected from among the twelve vibration amounts 1 orvibration amounts 2, and the track pitch, or a value in proportion to anaverage of m pieces of central values selected from the second powers ofthe twelve vibration amounts 1 or vibration amounts 2, and the trackpitch.
 12. An information disc recording/playback apparatus as definedin claim 7, wherein said rotation angle detection means divides therotation angle information of the disc rotation means into six areas forone rotation, and outputs the divided rotation angle information; andwhen a difference between the track cross count which is obtained at thefirst rotation speed for each of the six-divided rotation angles, andthe track cross count which is obtained with the at least one rotationspeed higher than the first rotation speed is represented byDAT[n]=DAT[0],DAT[1],DAT[2],DAT[3],DAT[4],DAT[5] (when n>5, n=n mod 6 (aremainder of n being divided by 6), and the rotation speed of the discrotation means is Vrpm[rpm], said control means determines a maximumrotation speed that is lower than the allowable amplitude of theinformation disc recording/playback apparatus, on the basis of a valuein proportion to a vibration speed 1 or a vibration speed 2, or a valuein proportion to the second power of the vibration speed 1 or the secondpower of the vibration speed 2, and the track pitch, said vibrationspeeds 1 and 2 being represented by $\begin{matrix}{{{vibration}\quad {speed}\quad {1\lbrack n\rbrack}} = {\frac{2\pi \quad V_{rpm}}{60}\quad \frac{2}{\sqrt{3}}\quad \sqrt{| {{{DAT}\lbrack n\rbrack}^{2} + {{{DAT}\lbrack n\rbrack}{{DAT}\lbrack {n + 1} \rbrack}} + {{DAT}\lbrack {n + 1} \rbrack}^{2}} |}}} & ( {{Formula}\quad 3} ) \\{{{vibration}\quad {speed}\quad {2\lbrack n\rbrack}} = {\frac{2\pi \quad V_{rpm}}{60}\frac{2}{\sqrt{3}}\sqrt{| {{{DAT}\lbrack n\rbrack}^{2} - {{{DAT}\lbrack n\rbrack}{{DAT}\lbrack {n + 2} \rbrack}} + {{DAT}\lbrack {n + 2} \rbrack}^{2}} |}}} & ( {{Formula}\quad 4} )\end{matrix}$


13. An information disc recording/playback apparatus as defined in claim12, wherein said control means determines a maximum rotation speed thatis lower than the allowable amplitude of the information discrecording/playback apparatus, on the basis of a value in proportion toan average of twelve vibration speeds 1 or vibration speeds 2 which arecalculated for n=0˜5 according to (Formula 3) and (Formula 4),respectively, and the track pitch, or a value in proportion to anaverage of m pieces of central values selected from the values of thetwelve vibration speeds 1 or vibration speeds 2, and the track pitch, ora value in proportion to an average of m pieces of central valuesselected from the second powers of the twelve vibration speeds 1 or thesecond powers of the vibration speeds 2, and the track pitch.
 14. Aninformation disc recording/playback apparatus as defined in claim 7,wherein said rotation angle detection means divides the rotation angleinformation of the disc rotation means into six areas for one rotation,and outputs the divided rotation angle information; and when adifference between the track cross amount which is measured at the firstrotation speed for each of the six-divided rotation angles, and thetrack cross amount which is measured with the at least one rotationspeed higher than the first rotation speed is represented byDAT[n]=DAT[0],DAT[1],DAT[2],DAT[3],DAT[4],DAT[5] (when n>5, n=n mod 6 (aremainder of n being divided by 6), and the rotation speed of the discrotation means is Vrpm[rpm], said control means determines a maximumrotation speed that is lower than the allowable amplitude of theinformation disc recording/playback apparatus, on the basis of a valuein proportion to a vibration acceleration 1 or a vibration acceleration2, or a value in proportion to the second power of the vibrationacceleration 1 or the second power of the vibration acceleration 2, andthe track pitch, said vibration accelerations. 1 and 2 being representedby $\begin{matrix}{{{vibration}\quad {acceleration}\quad {1\lbrack n\rbrack}} = {( \frac{2\pi \quad V_{rpm}}{60} )^{2}\frac{2}{\sqrt{3}}\sqrt{{{{DAT}\lbrack n\rbrack}^{2} + {{{DAT}\lbrack n\rbrack}{{DAT}\lbrack {n + 1} \rbrack}} + {{DAT}\lbrack {n + 1} \rbrack}^{2}}}}} & ( {{Formula}\quad 5} ) \\{{{vibration}\quad {acceleration}\quad {2\lbrack n\rbrack}} = {( \frac{2\pi \quad V_{rpm}}{60} )^{2}\frac{2}{\sqrt{3}}\sqrt{{{{DAT}\lbrack n\rbrack}^{2} - {{{DAT}\lbrack n\rbrack}{{DAT}\lbrack {n + 2} \rbrack}} + {{DAT}\lbrack {n + 2} \rbrack}^{2}}}}} & ( {{Formula}\quad 6} )\end{matrix}$


15. An information disc recording/playback apparatus as defined in claim14, wherein said control means determines a maximum rotation speed thatis lower than the allowable amplitude of the information discrecording/playback apparatus, on the basis of a value in proportion toan average of twelve vibration accelerations 1 or vibrationaccelerations 2 which are calculated for n=0˜5 according to (Formula 5)and (Formula 6), respectively, and the track pitch, or a value inproportion to an average of m pieces of central values selected from thevalues of the twelve vibration accelerations 1 or vibrationaccelerations 2, and the track pitch, or a value in proportion to anaverage of m pieces of central values selected from the second powers ofthe twelve vibration accelerations 1 or the second powers of the twelvevibration accelerations 2, and the track pitch.
 16. An information discrecording/playback apparatus as defined in claim 1, wherein said trackpitch detection means detects the type of the loaded information disc,and selects a track pitch corresponding to the detected disc type, withreference to a table in which standard track pitches corresponding tothe respective types of the information discs are described.
 17. Aninformation disc recording/playback apparatus as defined in claim 1further comprising: a move distance detection means for detecting thedistance by which the reading means moves; and said track pitchdetection means for making the reading means move for a predeterminedperiod of time or by a predetermined distance when the information discis loaded, counting the number of tracks the reading means crosses whileit is moving, and detecting the track pitch on the basis of the movedistance and the track cross count.
 18. An informationrecording/playback apparatus as defined in claim 1, further comprising:a linear speed detection means for detecting the linear speed of theinformation disc; a playback speed detection means for detecting thecurrent playback speed of the information disc; and said track pitchdetection means for calculating the track pitch of the information disc,on the basis of the detected type of the information disc, the linearspeed of the information disc detected by the linear speed detectionmeans, the playback speed detected at a predetermined rotation speed anda predetermined address, the predetermined rotation speed, thepredetermined address, the innermost radius of data area which is uniqueto the detected type of the disc, and the data rate when the disc isplayed at the predetermined playback speed which is unique to the typeof the disc.
 19. An information disc recording/playback apparatuscapable of recording or playing an information disc on which informationrecording tracks are formed spirally or concentrically, said apparatuscomprising: a disc rotation means for rotating the information disc at apredetermined speed; a reading means for reading an information signalfrom the disc; a drive means for driving the reading means in thedirection of the radius of the disc; a track cross detection means forgenerating track cross pulses on the basis of playback signals that aregenerated when the reading means crosses the information tracks; avariable filter means for preventing counting of pulses whose widths arenarrower than a set value, among the track cross pulses; a count meansfor counting the pulses outputted from the variable filter means; and acontrol means for determining a maximum rotation speed that is lowerthan an allowable number of track crosses of the information discrecording/playback apparatus on the basis of the count, or determining amaximum rotation speed that is lower than an allowable track cross speedor track cross acceleration of the information disc recording/playbackapparatus on the basis of the count and the current disc rotation speed,and controlling the disc rotation means so that the disc rotation meansrotates the information disc at a speed lower than the allowable maximumrotation speed to record or reproduce data in/from the disc.
 20. Aninformation disc recording/playback apparatus as defined in claim 19,further comprising: a track cross direction detection means fordetecting the track cross direction which indicates the direction inwhich the reading means crosses the information tracks; a rotation angledetection means for outputting rotation angle information of the discrotation means; and said count means for counting the track cross pulseswith signs, which are detected by the track cross detection means, onthe basis of the result of the detection by the track cross directiondetection means and the rotation angle information outputted from therotation angle detection means.
 21. An information discrecording/playback apparatus capable of recording or playing aninformation disc on which information recording tracks are formedspirally or concentrically, said apparatus comprising: a disc rotationmeans for rotating the information disc at a predetermined speed; areading means for reading an information signal from the disc; a drivemeans for driving the reading means in the direction of the radius ofthe disc; a track cross detection means for generating track crosspulses on the basis of playback signals that are generated when thereading means crosses the information tracks; a variable filter meansfor preventing counting of pulses whose widths are narrower than a setvalue, among the track cross pulses; a track cross direction detectionmeans for detecting the track cross direction which indicates thedirection in which the reading means crosses the information tracks; arotation angle detection means for outputting rotation angle informationof the disc rotation means; a count means including a first count meansfor counting the track cross pulses with signs, which are outputted fromthe filter means, on the basis of the result of the detection by thetrack cross direction detection means and the rotation angle informationoutputted from the rotation angle detection means, and a second countmeans for counting the track cross pulses outputted from the filtermeans, without detecting the track cross direction, on the basis of therotation angle information outputted from the rotation angle detectionmeans, said count means for obtaining the count of the first or secondcount means when an initial value of count is set for setting an initialvalue of the variable filter means, a value of the variable filter isset on the basis of the count and the current rotation speed, the drivemeans is disabled, and the information disc loaded on the disc rotationmeans is rotated at a predetermined rotation speed, and repeating theprocess of obtaining the count of the first or second count means whenthe value of the variable filter is set and the information disc isrotated at the predetermined speed, for a required number of times,thereby obtaining the counts for more than one rotation; and a controlmeans for determining a maximum rotation speed that is lower than anallowable number of track crosses of the information discrecording/playback apparatus on the basis of the count, or determining amaximum rotation speed that is lower than an allowable track cross speedor track cross acceleration of the information disc recording/playbackapparatus on the basis of the count and the current disc rotation speed,and controlling the disc rotation means so that the disc rotation meansrotates the information disc at a speed lower than the allowable maximumrotation speed to record or reproduce data in/from the disc.
 22. Aninformation disc recording/playback apparatus as defined in claim 21,wherein said count means obtains the count of the first count means whenthe value of the variable filter is set on the basis of the count andthe current rotation speed, the drive means is disabled, and theinformation disc loaded on the disc rotation means is rotated at apredetermined rotation speed, and repeats the process of obtaining thecount of the first count means when the information disc is rotated atthe predetermined speed, for a required number of times, therebyobtaining the counts for more than one rotation.
 23. An information discrecording/playback apparatus as defined in claim 21 or 22, wherein whensetting the value of the variable filter on the basis of the count andthe current rotation speed, if the count is one obtained withoutdetecting the track cross direction, assuming that the total number oftrack crosses per rotation is 4Tc, and the current rotation speed isVrpm, a maximum track cross speed is calculated by $\begin{matrix}{{{maximum}\quad {track}\quad {cross}\quad {speed}} = {\frac{2\pi \quad V_{rpm}}{60}T_{c}}} & ( {{Formula}\quad 7} )\end{matrix}$

and, on the basis of the calculated maximum track cross speed, the valueof the variable filter is set, and a minimum track count pulse width isset.
 24. An information disc recording/playback apparatus as defined inclaim 21 or 22, wherein said rotation angle detection means divides therotation angle information of the disc rotation means into six areas forone rotation and outputs the divided rotation angle information, andwhen the count is one obtained when the track cross direction isdetected, the count at each of the six-divided rotation angles isrepresented by DAT[n]=DAT[0],DAT[1],DAT[2],DAT[3],DAT[4],DAT[5] (whenn>5, n=n mod 6 (a remainder of n being divided by 6), and the rotationspeed of the disc rotation means is Vrpm[rpm], a value in proportion toa maximum track cross speed 1 or a maximum track cross speed 2 which arerepresented as follows are calculated as a maximum track cross speed,$\begin{matrix}{{{maximum}\quad {track}\quad {cross}\quad {speed}\quad {1\lbrack n\rbrack}} = {\frac{2\pi \quad V_{rpm}}{60}\frac{2}{\sqrt{3}}\sqrt{{{{DAT}\lbrack n\rbrack}^{2} + {{{DAT}\lbrack n\rbrack}{{DAT}\lbrack {n + 1} \rbrack}} + {{DAT}\lbrack {n + 1} \rbrack}^{2}}}}} & ( {{Formula}\quad 8} ) \\{{{maximum}\quad {track}\quad {cross}\quad {speed}\quad {2\lbrack n\rbrack}} = {\frac{2\pi \quad V_{rpm}}{60}\frac{2}{\sqrt{3}}\sqrt{{{{DAT}\lbrack n\rbrack}^{2} - {{{DAT}\lbrack n\rbrack}{{DAT}\lbrack {n + 2} \rbrack}} + {{DAT}\lbrack {n + 2} \rbrack}^{2}}}}} & ( {{Formula}\quad 9} )\end{matrix}$

and a value in proportion to an average of twelve maximum track crossspeeds 1 or maximum track cross speeds 2 which are calculated for n=0˜5according to (Formula 8) and (Formula 9), respectively, or a value inproportion to an average of m pieces of central values selected from thevalues of the twelve maximum track cross speeds 1 or maximum track crossspeeds 2, is employed as a maximum track cross speed.
 25. An informationdisc recording/playback apparatus as defined in claim 24, wherein whenthe value of the variable filter is set on the basis of the count andthe current rotation speed, if the count is one obtained when the trackcross direction is detected, the count at each of the six-dividedrotation angles is represented byDAT[n]=DAT[0],DAT[1],DAT[2],DAT[3],DAT[4],DAT[5] (when n>5, n=n mod 6 (aremainder of n being divided by 6), and the rotation speed of the discrotation means is Vrpm[rpm], a maximum track cross speed is calculatedon the basis of the following formulae, 4T _(c)=|DAT[0]|+|DAT[1]|+|DAT[2]|+|DAT[3]|+|DAT[4]|+|DAT[5]|  (Formula 10)$\begin{matrix}{{{maximum}\quad {track}\quad {cross}\quad {speed}} = {{\frac{2\pi \quad V_{rpm}}{60}T_{c}\frac{1}{\cos \frac{\pi}{6}}} = {\frac{2\pi \quad V_{rpm}}{60}T_{c}\frac{2}{\sqrt{3}}}}} & ( {{Formula}\quad 11} )\end{matrix}$

and, on the basis of the maximum track cross speed so calculated, thevalue of the variable filter is set, and a minimum track count pulsewidth is set.
 26. An information disc recording/playback apparatus asdefined in claim 19, wherein when setting the maximum rotation speed ofthe information disc recording/playback apparatus, the control meansemploys, as the count, a difference between the track cross count thatis obtained when the information disc is rotated at a first rotationspeed and at least one rotation speed that is higher than the firstrotation speed, and the count obtained with the at least one rotationspeed that is higher than the first rotation speed.
 27. An informationdisc recording/playback apparatus as defined in claim 19, wherein thetrack cross count is the number of track crosses which is calculated onthe basis of an average of counts corresponding to more than onerotation, which counts are selected from among the counts obtained bythe repetition.
 28. An information disc recording/playback apparatus asdefined in claim 27, wherein when calculating the track cross count, ifthe value of the variable filter means which is reset by repetition atthe same rotation speed changes by a predetermined value or more, thecounts obtained before the change are not used as the counts forcalculating the average.
 29. An information disc recording/playbackapparatus capable of recording or playing an information disc on whichinformation recording tracks are formed spirally or concentrically, saidapparatus comprising: a disc rotation means for rotating the informationdisc at a predetermined speed; a reading means for reading aninformation signal from the disc; a drive means for driving the readingmeans in the direction of the radius of the disc; a track crossdetection means for generating track cross signals on the basis ofplayback signals that are generated when the reading means crosses theinformation tracks; a pulse width storage means for holding the pulsewidth of a just-previous track cross signal; a filter means forcomparing the pulse width of the just previous track cross signal withthe pulse width of the current track cross signal, and preventing thecurrent track cross signal from being outputted when the current trackcross signal is reduced by a predetermined value or more; a count meansfor counting the pulses which are outputted from the variable filtermeans; and a control means for determining a maximum rotation speed thatis lower than an allowable number of track crosses of the informationdisc recording/playback apparatus on the basis of the obtained countsfor one or more rotation, or determining a maximum rotation speed thatis lower than an allowable track cross speed or track cross accelerationof the information disc recording/playback apparatus on the basis of theobtained counts for one or more rotation, and the current disc rotationspeed, and controlling the disc rotation means so that the disc rotationmeans rotates the information disc at a speed lower than the allowablemaximum rotation speed to record or reproduce data in/from the disc. 30.An information disc recording/playback apparatus as defined in claim 29,wherein said information disc recording/playback apparatus is able torecord or play two or more kinds of information discs having differenttrack pitches; and setting of the maximum rotation speed of theinformation disc recording/playback apparatus is performed by detectingthe track pitch of the information disc, and determining a maximumrotation speed that is lower than an allowable vibration amplitude ofthe information disc recording/playback apparatus on the basis of thecount and the track pitch, or determining a maximum rotation speed thatis lower than an allowable vibration speed or vibration acceleration ofthe information disc recording/playback apparatus on the basis of thecount, the track pitch, and the current disc rotation speed.
 31. Amethod for detecting vibrations of an information discrecording/playback apparatus capable of recording or playing at leasttwo kinds of information discs having different track pitches, on whichinformation recording tracks are formed spirally or concentrically, saidmethod comprising: a step of detecting the track pitch of theinformation disc; a step of counting track cross pulses on the basis ofplayback signals which are generated when the information disc fixedlyloaded on the apparatus is rotated and a reading unit crosses theinformation tracks on the information disc, thereby obtaining a count; astep of determining a maximum rotation speed that is lower than anallowable vibration amplitude of the information disc recording/playbackapparatus, on the basis of the obtained count and the track pitch; and astep of determining a maximum rotation speed that is lower than anallowable vibration speed or vibration acceleration of the informationdisc recording/playback apparatus, on the basis of the count, the trackpitch, and the current disc rotation speed.
 32. A method for detectingvibrations of an information disc recording/playback apparatus capableof recording or playing at least two kinds of information discs havingdifferent track pitches, on which information recording tracks areformed spirally or concentrically, said method comprising: a step ofdetecting the track pitch of the information disc; a step of detectingthe track cross direction indicating the direction in which a readingmeans crosses the information tracks; a step of outputting rotationangle information of the information disc, which is divided into n areasfor one rotation; a step of detecting two areas wherein the track crossspeed has the lowest value, from among the n-divided areas; a step ofcounting track cross pulses, which are based on playback signals thatare generated when the information disc fixedly loaded onto theapparatus is rotated and the reading means crosses the informationtracks on the information disc, such that the track cross pulses withsigns are counted while detecting the track cross direction in an areawhere the track cross speed has the lowest value, on the basis of thedetected track cross direction and the rotation angle information; astep of counting track cross pulses, which are based on playback signalsthat are generated when the information disc fixedly loaded onto theapparatus is rotated and the reading means crosses the informationtracks on the information disc, such that the track cross pulses withsigns are counted without detecting the track cross direction, on thebasis of the track cross direction which has just previously beendetected, in an area where the track cross speed does not have thelowest value; a step of determining a maximum rotation speed that islower than an allowable vibration amplitude of the information discrecording/playback apparatus, on the basis of the obtained count and thetrack pitch; and a step of determining a maximum rotation speed that islower than an allowable vibration speed or vibration acceleration of theinformation disc recording/playback apparatus, on the basis of thecount, the track pitch, and the current disc rotation speed.
 33. Amethod for detecting vibrations of an information discrecording/playback apparatus capable of recording or playing at leasttwo kinds of information discs having different track pitches, on whichinformation recording tracks are formed spirally or concentrically, saidmethod comprising: a step of detecting the track pitch of theinformation disc; a step of detecting the track cross directionindicating the direction in which a reading means crosses theinformation tracks; a step of outputting rotation angle information ofthe information disc, which is divided into n areas for one rotation; astep of detecting two areas wherein the track cross speed has the lowestvalue, from among the n-divided areas; a step of obtaining a first counton the basis of playback signals which are generated when theinformation disc fixedly loaded onto the apparatus is rotated and thereading means crosses the information tracks on the information disc; astep of obtaining a second count in which a sign is added to the count,on the basis of the track cross direction which has just previously beendetected, when the information disc is rotated; a step of selecting thefirst count in an area where the track cross speed has the lowest value,and selecting the second count in an area where the track cross speeddoes not have the lowest value, thereby counting the track cross pulsesfor every rotation angle and outputting the count; a step of determininga maximum rotation speed that is lower than an allowable vibrationamplitude of the information disc recording/playback apparatus, on thebasis of the obtained count and the track pitch; and a step ofdetermining a maximum rotation speed that is lower than an allowablevibration speed or vibration acceleration of the information discrecording/playback apparatus, on the basis of the count, the trackpitch, and the current disc rotation speed.
 34. A method for detectingvibrations of an information disc recording/playback apparatus capableof recording or playing at least two kinds of information discs havingdifferent track pitches, on which information recording tracks areformed spirally or concentrically, said method comprising: a step ofdetecting the track pitch of the information disc; a step of countingtrack cross pulses on the basis of playback signals which are generatedwhen the information disc fixedly loaded onto the apparatus is rotatedat a first rotation speed and a reading unit crosses the informationtracks on the information disc, thereby obtaining a count; a step ofcalculating a difference between a track cross count which is obtainedwhen the information disc is rotated with at least one rotation speedthat is higher than the first rotation speed, and a count which isobtained when the information disc is rotated at the first rotationspeed, thereby obtaining a difference count; a step of determining amaximum rotation speed that is lower than an allowable vibrationamplitude of the information disc recording/playback apparatus, on thebasis of the obtained difference count and the track pitch; and a stepof determining a maximum rotation speed that is lower than an allowablevibration speed or vibration acceleration of the information discrecording/playback apparatus, on the basis of the difference count, thetrack pitch, and the current disc rotation speed.
 35. A method fordetecting vibrations of an information disc recording/playback apparatuscapable of recording or playing an information disc on which informationrecording tracks are formed spirally or concentrically, said methodcomprising: a step of counting track cross pulses on the basis ofplayback signals which are generated when the information disc fixedlyloaded on the apparatus is rotated and a reading unit crosses theinformation tracks on the information disc, thereby obtaining a count; astep of comparing the widths of the detected track pulses with apredetermined value, and invalidating the counts of track pulses whosewidths are shorter than the predetermined value; a step of determining amaximum rotation speed that is lower than an allowable number of trackcrosses of the information disc recording/playback apparatus, on thebasis of the count; and a step of determining a maximum rotation speedthat is lower than an allowable track cross speed or track crossacceleration, on the basis of the count and the current disc rotationspeed.
 36. A method for detecting vibrations of an information discrecording/playback apparatus capable of recording or playing aninformation disc on which information recording tracks are formedspirally or concentrically, said method comprising: a step of countingtrack cross pulses on the basis of playback signals which are generatedwhen the information disc fixedly loaded on the apparatus is rotated anda reading unit crosses the information tracks on the information disc,thereby obtaining a count; a step of detecting the track cross directionindicating the direction in which the reading means crosses theinformation tracks; a step of outputting rotation angle information ofthe information disc; a step of comparing a set pulse width with thepulse width of the current track cross pulse, and invalidating the countof the current track cross pulse when its pulse width is decreased by apredetermined value or more; a first count step of counting the trackcross pulses with signs, whose widths are not decreased by thepredetermined value or more, on the basis of the track cross directionand the rotation angle information; a second count step of counting thetrack cross pulses whose widths are not decreased by the predeterminedvalue or more, without detecting the track cross direction, on the basisof the rotation angle information; a step of setting the set pulsewidths by repeating the steps of obtaining the first and second countsby a required number of times; a step of obtaining a count correspondingto one or more rotation of the information disc, by obtaining the countsobtained in the first and second count steps using the repeatedly setpulse widths; a step of determining a maximum rotation speed that islower than an allowable number of track crosses of the information discrecording/playback apparatus, on the basis of the count; and a step ofdetermining a maximum rotation speed that is lower than an allowabletrack cross speed or track cross acceleration, on the basis of the countand the current disc rotation speed.
 37. A method for detectingvibrations of an information disc recording/playback apparatus capableof recording or playing an information disc on which informationrecording tracks are formed spirally or concentrically, said methodcomprising: a step of counting track cross pulses on the basis ofplayback signals which are generated when the information disc fixedlyloaded on the apparatus is rotated and a reading unit crosses theinformation tracks on the information disc, thereby obtaining a count; astep of storing the pulse width of a track cross pulse which has justpreviously been detected; a step of comparing the stored track crosspulse width with the pulse width of the current track cross pulse, andinvalidating the count of the current track cross pulse when its pulsewidth is decreased by a predetermined value or more; a step ofdetermining a maximum rotation speed that is lower than an allowablenumber of track crosses of the information disc recording/playbackapparatus, on the basis of the count; and a step of determining amaximum rotation speed that is lower than an allowable track cross speedor track cross acceleration, on the basis of the count and the currentdisc rotation speed.